[2 Mark Question Answer]

Question 12 Marks

What effort will be required to lift a load of 500 N by a single movable pulley ? [Hint : Mechanical advantage of a single movable pulley is two],

Answer

Load = 500 N
Mechanical advantage (MA) = 2
of a single movable pulley
Effort = ?
We know that,
$M A=\frac{\text { Lord }}{\text { Effort }}$
⇒ Effort = \frac{500}{2}latex] N = 250 N

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Question 22 Marks

Calculate the mechanical advantage of a crowbar of length 240 cm if its fulcrum is situated at a distance of 40 cm from the load.

Answer

Length of crowbar = 240 cm
Length of load arm = 40 cm
Length of effort arm = 240 cm – 40 cm = 200 cm
Mechanical Advantage = $=\frac{\text { Load }}{\text { Effort }}=\frac{\text { Effort arm }}{\text { Load arm }}$
$\frac{200 cm }{40 cm }=5$

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Question 32 Marks

The length of the load arm of a lever is 6 m long and the effort arm is 3 m long. What is the effort required to lift a load of 40 N ?

Answer

Length of the load arm = 6 m
Length of the effort arm = 3 m
Load = 40N
Effort = ?
We know that .
$\frac{\text { Load }}{\text { Effort }}=\frac{\text { Effort arm }}{\text { Load arm }}$
By putting values, we get
$\begin{aligned} & \frac{40 N }{\text { Effort }}=\frac{3 m }{6 m } \\ \Rightarrow & \text { Effort }=\frac{40 \times 6}{3}=80 N \end{aligned}$

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Question 42 Marks

The length of a lever is 2 m. Calculate its mechanical advantage if the fulcrum is situated at a distance of 40 cm from the effort.

Answer

Length of the lever = 2m = 200 cm
Length of the effort arm = 40 cm
Length of the load arm = 200 cm – 40 cm = 160 cm
Mechanical advantage = ?
We know that,
Mechanical advantage = $=\frac{\text { Length of effort arm }}{\text { Length of load arm }}$
$MA =\frac{40 cm }{160 cm }=0.25$

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Question 52 Marks

Machines arc able to make our work convenient.

Answer

Machines help us to perform the same amount of work with much less effort than if we did the work manually. They also make our work faster and easier by multiplying the speed or the force applied.

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Question 62 Marks

State the principle of levers.

Answer

The principle of a lever states that the product of the load and the load arm is always equal to the product of the effort and the effort arm.

Load x Load arm = Effort x Effort arm

$\frac{\text { Load }}{\text { Effort }}=\frac{\text { Effort arm }}{\text { Load arm }}$

The above ratio is called the mechanical advantage of a lever.

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Question 72 Marks

What is a machine ?

Answer

Tools and objects that help us to perform the same amount of work with much less effort than if we did the work manually, are called machines. Example : lever, hammer, knife, etc

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Question 82 Marks

What do you understand by the term ‘efficiency of a machine’?

Answer

The ratio of the work done by the machine to the work done on the machine is called efficiency of a machine
Efficiency $=\frac{\text { Output energy }}{\text { Input energy }}$
[Work done by a machine is called the output energy and the work done on a machine is called the input energy.]

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Question 92 Marks

Using a suitable example, describe how a machine acts as a force multiplier.

Answer

It is very difficult to open the sealed metal cap of a cold drink bottle with our bare hands. A simple machine like a bottle opener (Class II lever) multiplies the applied force and much less effort is required to open the cap. Hence, it acts as a force multiplier.

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Question 102 Marks

What is the function of a screw ? Give any one use of a screw.

Answer

A screw is a special type of an inclined plane which has a sharp and pointed tip and can be turned (using a screw driver, bolt or a jack.) It acts as a force multiplier and less effort is required to do the work. Example : Screw forced and rotated into wood travels a greater distance with less effort than a nail would. Bolt rotating inside the fixed nut and jack used to lift a car use the principle of screw.

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PHYSICS [2 Mark Question Answer]

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