Work And Energy Test

Result

Work And Energy Test - 1

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Question 1
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A person carrying a load of 50 kg on his head moves 10 m on a straight horizontal road with acceleration of 2 m/s². The amount of work done by him is

A
500 joules

B
50 × 9.8 × 10 joules

C
zero

D
1000 joules

Solution

Resultant force acting on the person in the horizontal direction, F = ma

F = 50 × 2 = 100 N

W = Fs = 100 × 10 = 1000 joules
Question 2
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A truck and a car are moving on a smooth, level road such that the kinetic energy associated with them is the same. Brakes are applied simultaneously to both of them such that equal retarding force is produced in both. Which one will cover greater distance before it stops?

A
Car

B
Truck

C
Both will cover the same distance

D
Nothing can be decided

Solution

According to work-energy theorem, Work done = Change in the kinetic energy

W = F_s = Ff - K_i

As the change in kinetic energy is the same, the retarding force (F) will be the same.
So, the distance travelled by the car is the same as that travelled by the truck.
Question 3
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Let us assume that you have lifted a suitcase from the floor and kept it on a table. The work done by you on the suitcase depends on

A
the path taken by the suitcase

B
the time taken by you in doing so

C
the weight of the suitcase

D
your weight

Solution

Wok done against gravity is independent of the path followed, and it is equal to the change in the potential energy.
Change in the potential energy = mgh, hence work done depends upon mg (weight of the suitcase).