Q. 194.7( 3 Votes )

# A block of mass 5 Kg is lying on a frictionless table. A force of 20 N is applied on it for 10 seconds. Calculate its kinetic energy.

Answer :

Given,

Mass of body = 5 kg

Force F = 20 N

Time t = 10 seconds

To find: kinetic energy??

Initial velocity u = 0

Let final velocity be v

We know,

So, acceleration = 4 ms^{-2}

We also know that,

Substituting value of acceleration and u in this formula:

v = 10 s × 4 ms^{-2}

v = 40 ms^{-1}

Kinetic energy *=* *m v ^{2}*

*Substituting value of v in the equation*

*Kinetic energy =*

*= 4000 J*

*= 4 KJ*

Rate this question :

When a ball is thrown inside a mocking bus, does its kinetic energy depend on the speed of the bus? Explain.

Lakhmir Singh & Manjit Kaur - PhysicsFind the momentum of a body of mass 100 g having a kinetic energy of 20 J.

Lakhmir Singh & Manjit Kaur - PhysicsA man drops a 10 kg rock from the top of a 5 m ladder. What is its speed jest before it hits the ground? What is its kinetic energy when it reaches the ground? (g = 10 m/s^{2})

On a level road, a scooterist applies brakes to slow down from a speed of 10 m/s to 5 m/s. If the mass of the scooterist and the scooter be 150 kg, calculate the work done by the brakes. (Neglect air resistance and friction)

Lakhmir Singh & Manjit Kaur - PhysicsA bullet of mass 15 g has a speed of 400 m/s. What is its kinetic energy? If the bullet strikes a thick target and is brought to rest in 2 cm, calculate the average net force acting on the bullet. What happens to the kinetic energy originally in the bullet?

Lakhmir Singh & Manjit Kaur - PhysicsA light and a heavy object have the same momentum. Find out the ratio of their kinetic energies. Which one has a larger kinetic energy?

NCERT Science - ExemplarA car is accelerated on a leveled road and attains a speed of 4 times its initial speed. In this process, the kinetic energy of the car:

A. Does not change

B. Becomes 4 times that of initial kinetic energy

C. Becomes 8 times that of initial kinetic energy

D. Becomes 16 times that of initial kinetic energy

Lakhmir Singh & Manjit Kaur - Physics