Q. 104.1( 127 Votes )

# An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half way down (g = 10 m/s^{2})

Answer :

Given,

Mass, *m* = 40 kg

Acceleration due to gravity, *g* = 10 m/s^{2}

Height, *h* = 5 m

We know that,

Potential energy = *m* × *g* × *h*

= 40 × 10 × 5

= 2000 J

When the object is fall to its half way down, then its height above the ground =

=2.5 m

Now, Potential energy = *m* × *g* × *h*

= 40 × 10 × 2.55 J

= 1000 J

Now, we know that according to the law of conservation of energy:

Total potential energy = Potential energy at half way down + Kinetic energy at half way down

2000 = 1000 + Kinetic energy at half way down

Kinetic energy at half way down = 2000 – 1000

= 1000 J

Rate this question :

If 784 J of work was done in lifting a 20 kg mass, calculate the height through which it was lifted. (g = 9.8 m/s^{2})

An object of mass 5 kg falls from a height of 5 m above the ground. The loss of potential energy of the mass is :

Evergreen - ScienceState whether the following statement is true or false:

The potential energy of a body of mass 1 kg kept at a height of 1m is 1J.

Lakhmir Singh & Manjit Kaur - PhysicsA body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential energy at the end of 2 s? (Assume g = 10 m/s^{2}).

A girl weighing 400 N climbs a vertical ladder. If the value of g be 10 m s^{-2}, the work done by her after climbing 2 m will be:

A. 200 J B. 800 J

C. 8000 J D. 2000 J

Lakhmir Singh & Manjit Kaur - PhysicsWater stored in a dam possesses:

A. No energy

B. Electrical energy

C. Kinetic energy

D. Potential energy

Lakhmir Singh & Manjit Kaur - PhysicsA car is accelerated on a leveled road and acquires a velocity 4 times of its initial velocity. During this process, the potential energy of the car:

A. Does not change

B. Becomes twice that of initial potential energy

C. Becomes 4 times that of initial potential energy

D. Becomes 16 times that of initial potential energy.

Lakhmir Singh & Manjit Kaur - Physics