Question

An object of mass 40kg is raised to a height of 5m above the ground. What is it's potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down .​

Answer 1

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At a height of 5 metre object has a potential energy of 2000 J. When this object is allowed to fall and it is Half way down its height above the ground will be half of 5 m= 5/2= 2.5m. Potential Energy at Half way down= 1000 joules. Kinetic energy at half way down= 1000 joules.

Answer 2

GIVEN :

• Mass, m = 40 kg
• Gravity, g = 10 m/s²
• Height, h = 5 m

TO FIND :

• Kinetic energy (KE) when it is half way down = ?

FORMULA USED :

• PE = mgh

Where,

PE = potential energy.

m = mass.

g = acceleration due to gravity.

h = height.

SOLUTION :

We know that , Potential energy (PE) = mgh.

PE = m × g × h

PE = 40 × 10 × 5

PE = 2000 J

PE at half way down,

PE = mgh

PE = 40 × 10 × 2.5 ...... { Here h = 2.5 because h =5/2 - Half way down }

PE = 1000 J

PE at half way down = 1000 J.

KE at half way down = 2000 - 1000 J

KE at half way down = 1000 J

KE at half way down = 1000 J.