Question

Q. An object of mass 20kg is raised to a height of 10 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=10m/s​

Answer 1

Explanation:

Given:-

• Mass ,m = 20 kg
• Height, h = 10m
• Acceleration due to gravity ,g = 10m/s²

To Find:-

• Potential Energy ,PE
• Kinetic Energy when it is half way down ,KE

Solution:-

As we have to calculate the potential energy of the object .

Potential Energy is defined as the energy possess by body due to its position .

• PE = mgh

where,

• m denote mass
• g denote acceleration due to gravity
• h denote height

Substitute the value we get

→ PE = 20×10×10

→ PE = 2000J

• Hence, the potential energy of the object at given position is 2000 joules.

Now, As we know that the law of conservation of energy state that energy can neither be created or nor be destroyed it can be transferred from one state to another.

Here , the potential energy of the object is converted into the kinetic energy .

• KE = PE = mgh

when the object come half of its initial position then its new position is 10/2 = 5m

So, the kinetic energy of the object at half of the initial position is

• KE = mgh

substitute the value we get

→ KE = 20×10×5

→ KE = 200 × 5

→ KE = 1000 J

• Hence, the kinetic energy of the object in half position is 1000 joules .

Answer 2

Answer:

Given :-

• Mass (M) = 20 kg
• Height (H) = 10 m
• Acceleration (A) = 10 m/s

To Find :-

• PE
• KE at half height

Solution :-

We know that

PE = mgh

PE = Potential Energy

M = Mass

G = Acceleration due to gravity

H = Height

PE = 20 × 10 × 10

PE = 20 × 100

PE = 2000 J

Now,

When height is half

So,

10/2 = 5 m

Now,

PE = KE

KE = mgh

KE = Kinetic Energy

M = Mass

G = Acceleration due to gravity

H = Height

KE = 20 × 10 × 5

KE = 20 × 50

KE = 1000 J

So,

PE = 2000 J

KE (half height) = 1000 J