I. Select the correct option:
1. In
a lever of class I [Recall]
o (a) the
fulcrum lies between the load and the effort
o (b)
the load lies between the fulcrum and the effort
o (c) the effort lies between the load and the fulcrum
o (d) all of the above are correct
o Answer: (a)
2. Which
statement is not true for a simple machine? [Understanding]
o (a) It makes work easy
o (b) It multiplies force
o (c) It saves energy
o (d) It saves time
o Answer: (c)
3. A
beam balance is a lever of [Application]
o (a) class I
o (b) class II
o (c) class III
o (d) none of these
o Answer: (a)
4. Which
of the following statements is incorrect for an ordinary fixed pulley? [Recall]
o (a) It is a lever of class II
o (b) Effort is greater than load
o (c) Effort is equal to load
o (d) None of these
o Answer: (a)
5. Wheel
is used with axle because [Application]
o (a) sliding friction is less than the rolling friction
o (b) rolling friction is less than the sliding friction
o (c) they work as the inclined plane
o (d) they help to change the direction of the force
o Answer: (b)
II. Assertion and
Reasoning Questions
Codes: (a) Both True, (b) Both False, (c) A is false,
R is true, (d) A is true, R is false.
1. Assertion (A): A first-class lever has the
fulcrum located between the input and output forces.
o Answer: (d)
2. Assertion (A): In a practical simple
machine, work done by the effort is always equal to the work done on the load.
o Answer: (b)
3. Assertion (A): A wheel and axle is a simple
machine used for increasing speed and changing the direction of force.
o Answer: (d)
4. Assertion (A): A screw is an example of a
simple machine used for lifting heavy loads.
o Answer: (a)
5. Assertion (A): A pulley is an example of a
simple machine that changes the direction of force.
o Answer: (d)
III. Fill in the blanks
with the correct option:
1. In
a lever of class I, the fulcrum
is in the middle.
2. The crowbar is the lever of class I.
3. The force applied to move an object is called effort.
4. A pulley changes the direction of a force.
5. The outer parts of a machine are painted to protect
them from rusting.
IV.
True or False
1. A machine can do
work by itself.
o False. Correct: A machine requires
energy supplied to it (input) to produce work (output)
2. A stapler is a complex machine.
o False. Correct: A stapler is an
example of a class III simple machine
3. A lemon squeezer is a lever of class III.
o False. Correct: A lemon squeezer is
a lever of class II
4. A pulley is a grooved wheel.
o True.
5. A wheel and axle is a simple machine made up of
two identical cylinders.
o False. Correct: It consists of a
big cylinder (wheel) joined to a small cylinder (axle)
V.
Match the following:
1. Wheelbarrow — (c) Lever of class II
2. A pulley — (a) Changes the direction
of force
3. Beam balance — (b) Lever of class I
4. Tweezers — (d) Lever of class III
5. Wheel and axle — (e) Rolls heavy loads
VI.
Pick the odd one out.
1. Screw driver,
sewing machine, bicycle, mixer grinder.
o Odd One: Screw driver. It is a simple machine
2. Shovel, knife, human arm, crowbar.
o Odd One: Crowbar. It is a class I lever
3. Bottle opener, nut cracker, plier, wheelbarrow.
o Odd One: Plier. It is a class I lever
VII.
Answer the following in one word/one statement:
1. State the principle
of levers.
o Load × Load arm = Effort × Effort arm.
2. What is the advantage of using a pulley?
o It allows work to be done more conveniently by
applying effort in a downward direction to lift a load
3. Why is oiling of some parts of a machine
necessary?
o Oiling (lubrication) is necessary to reduce
friction between moving parts and prevent wear and tear
4. How
is a machine taken care of in the following cases? (a) The axle of pulley fixed on a well may not wear
out.
o The moving parts (axle) should be regularly
lubricated with oil or grease
5. · (a) Axle of pulley:
Regular lubrication with oil or grease. (b) Bicycle handle: Protecting
from moisture and painting to prevent rusting. (c) Delicate machines:
Keeping them covered to protect from dirt and dust.
6. · Class of lever in
wheelbarrow: Class II lever.
7. · Fishing rod: Class III
lever.
8. · MA greater than one: Class
II levers.
9. · Can effort be greater than
load? Yes, in class III levers.
10.
·
Simple machine with two inclined planes: A wedge.
11.
·
Force causing wear and tear: Friction.
VIII. Define the following
terms:
1.
Mechanical Advantage:
- Mechanical Advantage (MA) is the ratio of
the load to the effort in a machine.
- It indicates how much a machine multiplies
the applied force.
- Formula: MA = Load / Effort
2.
Velocity Ratio:
- Velocity Ratio (VR) is the ratio of the
velocity of effort to the velocity of the load in a machine.
- It is also defined as the ratio of the
distance moved by the effort to the distance moved by the load.
- Formula: VR = Velocity of Effort /
Velocity of Load
3.
Ideal Machine:
- An ideal machine is a theoretical machine
in which the work done by the machine (output) is equal to the work done
on the machine (input).
- In an ideal machine, there is no loss of
energy due to friction or other factors.
4.
Efficiency:
- Efficiency is the ratio of the work done
by the machine (output) to the work done on the machine (input), expressed
as a percentage.
- It indicates how effectively a machine
converts input energy into useful output energy.
- Formula: Efficiency (%) = (Output Work /
Input Work) × 100
IX. Answer the following
questions in short:
1.
What is a machine? Why do we use machines?
- A machine is a device that makes work
easier by multiplying the applied force or changing the direction of the
force.
- We use machines to reduce the effort
required to perform tasks, save time, and increase efficiency.
2.
How is a wheel a simple machine?
- A wheel is a simple machine because it
reduces friction, making it easier to move objects.
- It converts sliding friction into rolling
friction, which requires less force to move heavy loads.
- Example: Wheels on a cart or bicycle help
in moving heavy objects smoothly.
IX. Answer the following
questions in short:
3.
State the different types of levers. Give two examples of each.
·
Class
I Lever:
- Fulcrum is between the load and the
effort.
- Examples:
- See-saw
- Scissors
·
Class
II Lever:
- Load is between the fulcrum and the
effort.
- Examples:
- Wheelbarrow
- Nutcracker
·
Class
III Lever:
- Effort is between the fulcrum and the
load.
- Examples:
- Tweezers
- Fishing rod
4.
State whether a pulley can be considered a lever. Justify your answer.
- Yes, a pulley can be considered a type of
lever.
- Justification:
- A pulley changes the direction of the force
applied, similar to how a lever does.
- The fulcrum of a pulley is the point where the
pulley is fixed, the load is the object being lifted, and the effort is
the force applied to the rope.
- The principle of a pulley is analogous to that
of a lever, where the mechanical advantage can be achieved by changing
the direction or magnitude of the force.
5.
What do you understand by a wheel and axle? Give two examples.
·
Wheel
and Axle:
- A wheel and axle is a simple machine consisting
of a large wheel attached to a smaller axle so that these two parts
rotate together.
- The wheel is the larger part that force is
typically applied to, and the axle is the smaller part that force is
exerted on by the wheel.
·
Examples:
- Bicycle wheel
- Steering wheel of a car
6.
List two ways in which a screw is more useful than a nail.
- Advantages of a screw over a nail:
- A screw provides a stronger hold and is less
likely to come loose compared to a nail.
- A screw can be easily removed and reused,
whereas a nail often bends or damages the material when removed.
7.
Why is proper care of machines essential? Give any three points in support of
your answer.
- Importance of proper care of machines:
- Prevents Rusting: Regular maintenance, such as painting and
oiling, prevents rusting of metal parts.
- Reduces Wear and Tear: Lubrication of moving parts reduces friction,
which minimizes wear and tear.
- Increases Lifespan: Proper care and maintenance increase the
efficiency and lifespan of machines, ensuring they function effectively
for a longer period.
X. Answer the following
questions in detail:
1.
Explain the working of a wheel and axle system in brief. How can the handle of
a bicycle be considered as an example of wheel and axle system?
·
Working
of a Wheel and Axle System:
- A wheel and axle system consists of a large
wheel attached to a smaller axle. When force is applied to the wheel, it
rotates and causes the axle to rotate as well.
- The mechanical advantage of a wheel and axle
system is achieved because the force applied to the larger wheel results
in a greater force being exerted by the smaller axle.
·
Bicycle
Handle as an Example:
- The handle of a bicycle is connected to the
front wheel through the axle.
- When the handle is turned, it rotates the axle,
which in turn rotates the wheel, allowing the bicycle to change
direction.
- This system allows for easier control and
maneuverability of the bicycle.
2.
Explain the principle of working of a wedge with the help of a suitable
example.
·
Principle
of a Wedge:
- A wedge is a simple machine that consists of two
inclined planes joined together.
- It works by converting the force applied on its
wide end into a force directed outwards along its slope, which can split
or cut objects.
·
Example:
- Axe:
- When an axe is used to chop wood, the force
applied to the wide end of the axe head drives the sharp edge (wedge)
into the wood.
- The wedge shape of the axe head splits the wood
apart by exerting a force outward along the slope of the wedge.
- This makes it easier to split the wood compared
to applying force directly with a blunt object.
3. Describe
three simple machines and provide real-life examples of each. How do these
machines make tasks easier for us?
·
Lever:
- Description: A lever is a rigid bar that rotates around a
fixed point called the fulcrum. It is used to lift or move loads with
less effort.
- Example: See-saw, crowbar.
- How it makes tasks easier: Levers allow us to lift heavy objects with less
effort by distributing the load over a longer distance from the fulcrum.
·
Pulley:
- Description: A pulley is a wheel with a groove along its
edge where a rope can run. It is used to lift heavy objects by changing
the direction of the force applied.
- Example: Flagpole pulley, construction cranes.
- How it makes tasks easier: Pulleys make lifting heavy objects easier by
allowing the force to be applied in a more convenient direction and
reducing the amount of force needed.
·
Wheel and
Axle:
- Description: A wheel and axle is a simple machine consisting
of a large wheel attached to a smaller axle so that these two parts
rotate together.
- Example: Bicycle wheel, car steering wheel.
- How it makes tasks easier: The wheel and axle system reduces friction and
makes it easier to move heavy loads by rolling instead of sliding.
XI. Differentiate between the following:
1. Movable Pulley and Fixed Pulley:
2. Levers of Class I, II, and III:
3. Pulley and Wheel and Axle:
XII. Numericals:
1. A load of 120 N is kept at a
distance of 1.5 m from the fulcrum of a lever. At what distance should an
effort of 40 N be applied to balance the lever?
·
Given:
- Load
(L) = 120 N
- Load
arm = 1.5 m
- Effort
(E) = 40 N
- Effort
arm = ?
2. What minimum effort is needed to lift a load of 150 N using a lever whose mechanical advantage is 1.5?
-
Given:
- Load (L) = 150 N
- Mechanical Advantage (MA) = 1.5
- Effort (E) = ?
3. A crowbar of length 10 m has a fulcrum at a distance of 4 m from one end. Calculate the effort required to lift a load of 120 N.
-
Given:
- Length of crowbar = 10 m
- Distance of fulcrum from one end (load arm) = 4 m
- Distance of fulcrum from the other end (effort arm) = 10 m - 4 m = 6 m
- Load (L) = 120 N
4. From the following data, determine the unknown quantity:
(a) Load = 450 N, effort = 150 N, mechanical advantage = ?
-
Given:
- Load (L) = 450 N
- Effort (E) = 150 N
-
5. The length of a lever of class I is 4 m. Calculate the mechanical advantage of the lever if its fulcrum is located at a distance of 120 cm from the effort.
-
Given:
- Length of lever = 4 m = 400 cm
- Distance of fulcrum from effort = 120 cm
- Distance of fulcrum from load (Load arm) = 400 cm - 120 cm = 280 cm
-
-
Here are the solutions to the numerical problems and the HOTS question:
XII. Numericals:
3. A crowbar of length 10 m has a fulcrum at a distance of 4 m from one end. Calculate the effort required to lift a load of 120 N.
-
Given:
- Length of crowbar = 10 m
- Distance of fulcrum from one end (load arm) = 4 m
- Distance of fulcrum from the other end (effort arm) = 10 m - 4 m = 6 m
- Load (L) = 120 N
-
Using the principle of levers:
- Answer: 80 N
4. From the following data, determine the unknown quantity:
(a) Load = 450 N, effort = 150 N, mechanical advantage = ?
-
Given:
- Load (L) = 450 N
- Effort (E) = 150 N
-
Using the formula for mechanical advantage:
- Answer: 3
(b) Mechanical advantage = 0.3, effort = 80 N, load = ?
-
Given:
- Mechanical Advantage (MA) = 0.3
- Effort (E) = 80 N
-
Using the formula for mechanical advantage:
- Answer: 24 N
5. The length of a lever of class I is 4 m. Calculate the mechanical advantage of the lever if its fulcrum is located at a distance of 120 cm from the effort.
-
Given:
- Length of lever = 4 m = 400 cm
- Distance of fulcrum from effort = 120 cm
- Distance of fulcrum from load (Load arm) = 400 cm - 120 cm = 280 cm
-
Using the formula for mechanical advantage:
- Answer: 2.33
HOTS and Critical Thinking:
1. Imagine you are designing a playground for children. How could you incorporate different types of levers or simple machines to make the playground more interactive and fun?
-
See-saw:
- Type: Class I Lever
- Implementation: Install see-saws of different lengths to demonstrate how the position of the fulcrum affects the balance and effort needed to lift a friend.
-
Slides:
- Type: Inclined Plane
- Implementation: Use slides of varying slopes to show how the angle of the slide affects the speed and ease of sliding down.
-
Merry-go-round:
- Type: Wheel and Axle
- Implementation: Incorporate a merry-go-round to demonstrate rotational motion and how the wheel and axle system works.
-
Swings with pulleys:
- Type: Pulley System
- Implementation: Use pulleys to allow children to lift small buckets of sand or water, demonstrating how pulleys can change the direction of force and make lifting easier.
-
Jungle Gym with Levers:
- Type: Class III Lever
- Implementation: Design climbing bars or ladders that act as levers, showing how effort is applied between the fulcrum and the load.
Let's solve the questions one by one:
2. Ravi and Savita Scenario:
(a) Identify the levers and their types mentioned in the passage.
-
See-saw:
- Type: Class I Lever
- Explanation: The fulcrum is in the middle, with Ravi and Savita sitting on either side applying effort and acting as loads.
-
Wheelbarrow:
- Type: Class II Lever
- Explanation: The load (leaves and garbage) is between the fulcrum (wheel) and the effort (gardener's hands).
-
Lemon Squeezer:
- Type: Class II Lever
- Explanation: The load (lemon) is between the fulcrum (hinge) and the effort (hand squeezing the handles).
-
Tongs:
- Type: Class III Lever
- Explanation: The effort (hand holding the tongs) is between the fulcrum (pivot point) and the load (ice pieces).
(b) Draw the diagram of each lever and label fulcrum, load, and effort.
Since I can't draw here, I'll describe how you can draw each diagram:
-
See-saw:
- Draw a long plank balanced on a triangular fulcrum in the middle.
- Label the fulcrum in the center.
- Label the load and effort on either side of the fulcrum.
-
Wheelbarrow:
- Draw a wheelbarrow with a wheel at the front.
- Label the wheel as the fulcrum.
- Label the load (leaves and garbage) in the middle of the wheelbarrow.
- Label the effort at the handles where the gardener applies force.
-
Lemon Squeezer:
- Draw a lemon squeezer with two handles and a hinge in the middle.
- Label the hinge as the fulcrum.
- Label the lemon in the middle as the load.
- Label the effort at the ends of the handles where force is applied.
-
Tongs:
- Draw a pair of tongs with a pivot point in the middle.
- Label the pivot point as the fulcrum.
- Label the ice pieces at the end of the tongs as the load.
- Label the effort at the handles where force is applied.
3. Pulley Diagram:
(a) What kind of pulleys are A and B?
- A: Movable Pulley
- B: Fixed Pulley
(b) State the purpose of pulley B.
- Purpose of Pulley B:
- Pulley B is a fixed pulley. Its purpose is to change the direction of the force applied.
- It allows the user to pull down to lift the load, making it more convenient to apply force.
(c) What effort has to be applied at C to just raise the load L = 20 kgf?
-
Given:
- Load (L) = 20 kgf
- Pulley A is a movable pulley, which provides a mechanical advantage of 2.
-
4. Definition of a Machine:
-
Definition:
- A machine is a device that makes work easier by either multiplying the applied force or changing the direction of the force.
-
Example:
- Lever: A see-saw is a simple machine that allows children to lift each other by applying force at different points along the lever.
- Pulley: A flagpole pulley allows someone to raise a flag by pulling down on a rope, changing the direction of the force applied.
Here are the answers to the questions in the image:
5. An electric fan is made up of several simple machines. Where would you find an inclined plane on a fan? Also, mention where you would find a wheel and axle on it.
-
Inclined Plane:
- The blades of an electric fan are shaped like inclined planes. They are angled to push air downward or forward as they rotate.
-
Wheel and Axle:
- The rotating part of the fan, where the blades are attached to the central hub, acts as a wheel and axle. The blades form the wheel, and the central rod or motor shaft acts as the axle.
-
Diagram-based Questions
1. Identify Fulcrum (F), Load (L), and Effort (E)
In these levers, the positions are determined by which part is fixed (fulcrum), where the work is being done (load), and where you apply force (effort).
(a) Wheelbarrow: * F: The wheel (the pivot point).
L: The center of the tub where the weight sits.
E: The handles where the person lifts.
(b) Nutcracker: * F: The joint where the two arms meet.
L: The nut in the middle.
E: The ends of the handles where you squeeze.
(c) Bottle Opener: * F: The tip that rests on top of the bottle cap.
L: The hook that catches the edge of the cap.
E: The handle where you pull upward.
(d) See-saw: * F: The center support beam.
L: One person (the one being lifted).
E: The other person (the one pushing down).
Here are the answers to the questions in the image:
5. An electric fan is made up of several simple machines. Where would you find an inclined plane on a fan? Also, mention where you would find a wheel and axle on it.
-
Inclined Plane:
- The blades of an electric fan are shaped like inclined planes. They are angled to push air downward or forward as they rotate.
-
Wheel and Axle:
- The rotating part of the fan, where the blades are attached to the central hub, acts as a wheel and axle. The blades form the wheel, and the central rod or motor shaft acts as the axle.
Diagram-based Questions:
1. In the following simple machines, mark the position of fulcrum, load, and effort. Use letter L for load, E for effort, and F for fulcrum.
-
(a) Wheelbarrow:
- Fulcrum (F): The wheel of the wheelbarrow.
- Load (L): The contents inside the wheelbarrow.
- Effort (E): The handles where the person applies force.
-
(b) Stapler:
- Fulcrum (F): The pivot point where the stapler's top part is attached.
- Load (L): The staples being pushed out.
- Effort (E): The point where you press down on the stapler.
-
(c) Nutcracker:
- Fulcrum (F): The hinge of the nutcracker.
- Load (L): The nut being cracked.
- Effort (E): The handles where you apply force.
-
(d) See-saw:
- Fulcrum (F): The central pivot point.
- Load (L): The person or weight on one side.
- Effort (E): The person or weight on the other side applying force.
2. Observe the figures given below and answer the questions that follow:
-
(a) Which of the figures given below is an example of a combination of two simple machines?
- (ii) The figure of the woman drawing water from the well is an example of a combination of a wheel and axle (the well pulley) and a lever (the handle she is turning).
-
(b) Where is the force usually applied in (i)?
- In the knife (i), the force is usually applied to the handle, which acts as the effort.
-
(c) What is the main use of a simple machine used in (ii)?
- The simple machine in (ii) is used to draw water from the well. The pulley system makes it easier to lift the heavy bucket of water.
-
(d) How is a simple machine used in (iii) a force multiplier?
- The simple machine in (iii) is a yo-yo, which uses the principle of the wheel and axle. When you pull the string, the axle rotates, allowing the yo-yo to spin and move up and down with less effort due to the mechanical advantage provided by the wheel and axle system.
Case-based OR Passage-based Questions:
1. In the following figure, a broom is shown:
-
(a) Identify the category of simple machine this object belongs to.
- The broom is a Class III lever.
-
(b) Calculate the mechanical advantage of the broom.
- Given:
- Effort arm = 1.2 m
- Load arm = 0.3 m
- Answer: 4
- Given:
-
-
(c) Is the value calculated in part (b) less than one? Discuss the importance of the broom based on the result found in part (b).
- No, the mechanical advantage is 4, which is greater than one.
- Importance: The broom's mechanical advantage being greater than one means that it allows the user to apply less effort to move a larger load (dirt or debris) over a longer distance, making cleaning more efficient.
Case-based OR Passage-based Questions:
1. In the following figure, a broom is shown:
(a) Identify the category of simple machine this object belongs to.
- The broom is a Class III Lever.
(b) Calculate the mechanical advantage of the broom.
-
Given:
- Effort arm (distance from the fulcrum to where you hold the broom) = 1.2 m
- Load arm (distance from the fulcrum to the broom head) = 0.3 m
-
Using the formula for mechanical advantage:
- Answer: The mechanical advantage of the broom is 4.
(c) Is the value calculated in part (b) less than one? Discuss the importance of the broom based on the result found in part (b).
-
No, the mechanical advantage is not less than one; it is 4.
-
Importance:
- A mechanical advantage greater than one means that the broom allows you to apply less effort to move a larger load (dirt or debris) over a longer distance.
- This makes sweeping more efficient and less strenuous, as you can move more dirt with less effort.
2. Maya and Alex are exploring their surroundings to identify simple machines in their daily lives.
(a) Describe three different types of simple machines and provide examples from your daily life for each type.
-
Lever:
- Description: A lever is a rigid bar that rotates around a fixed point called the fulcrum.
- Example: See-saw, broom, crowbar.
-
Pulley:
- Description: A pulley is a wheel with a groove along its edge where a rope can run. It is used to lift and move loads.
- Example: Flagpole pulley, construction cranes, window blinds.
-
Wheel and Axle:
- Description: A wheel and axle is a simple machine consisting of a large wheel attached to a smaller axle so that these two parts rotate together.
- Example: Bicycle wheel, car steering wheel, doorknob.
(b) Explain how these simple machines make tasks easier.
-
Lever:
- Levers allow us to lift or move heavy loads with less effort by distributing the load over a longer distance from the fulcrum.
-
Pulley:
- Pulleys make lifting heavy objects easier by allowing the force to be applied in a more convenient direction and reducing the amount of force needed.
-
Wheel and Axle:
- The wheel and axle system reduces friction and makes it easier to move heavy loads by rolling instead of sliding.
(c) Discuss the concept of mechanical advantage in the context of simple machines.
- Mechanical Advantage (MA):
- Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device, or machine system.
- It is the ratio of the load (the force exerted by the machine) to the effort (the force applied to the machine).
- Formula:
- A higher mechanical advantage means that the machine allows you to lift or move a heavier load with less effort.
Experiential Learning Questions:
1. Create a lever set-up using a ruler or a wooden plank as the lever, a fulcrum (pencil or similar), and a known weight.
(a) Describe the lever set-up you created for the experiment.
-
Materials Needed:
- A ruler or wooden plank (lever)
- A pencil or similar object (fulcrum)
- A known weight (e.g., a book or a small weight)
-
Set-up:
- Place the pencil under the ruler to act as the fulcrum.
- Place the known weight at one end of the ruler.
- Apply force at the other end of the ruler to lift the weight.
(b) Use the measurements to calculate the mechanical advantage of the lever in each set-up.
-
Measurements:
- Measure the distance from the fulcrum to the weight (load arm).
- Measure the distance from the fulcrum to where you apply force (effort arm).
-
Using the formula for mechanical advantage:
(c) Explain how the mechanical advantage changes as you adjust the positions of the fulcrum and the weight.
-
Observation:
- When the fulcrum is closer to the weight, the effort arm becomes longer, increasing the mechanical advantage.
- When the fulcrum is closer to where you apply force, the load arm becomes longer, decreasing the mechanical advantage.
-
Conclusion:
- The mechanical advantage increases as the effort arm lengthens or the load arm shortens.
- Conversely, the mechanical advantage decreases as the effort arm shortens or the load arm lengthens.
Across:
2. The ratio of work output to the work input:
- Efficiency
5. A simple machine used to lift a load up:
- Pulley
6. The ability to do work:
- Energy
7. The weight lifted by a machine:
- Load
8. An applied force to bring desired change to the position (push or lift) of the load:
- Effort
Down:
1. The distance between two threads:
- Pitch
3. A fixed point about which a machine turns while doing work:
- Fulcrum
4. Modified form of inclined plane which carries people between floors of a building:
- Escalator
Comments
Post a Comment