Question

A body mass of 2kg was dropped from the top of the building. It had kinetic energy of 900J .Find the height of the building

Answer 1

Answer:

45m

Explanation:

I am not sure but here you go,

K.E=mgh

900=2x10(g)xh

900=20xh

900/20=h

45=h

Answer 2

45.92 m is the required answer.

GIVEN:

• Mass of the body, m = 2 kg

• Kinetic energy, k = 900 J

TO FIND:

Height of the building, h

FORMULA:

According to law of conservation of energy,

total energy remains constant.

Total energy = potential energy + kinetic energy

Potential energy = mgh

Kinetic energy = (mv²)/2

Where,

• g is the acceleration due to gravity ,g = 9.8 m/s²
• v is the velocity.

SOLUTION:

When the body is at height h ,it is at rest. At this point velocity is zero .

v = 0

Kinetic energy = (mv²)/2

Kinetic energy = (m × 0 )/2

Kinetic energy = 0

So kinetic energy is also zero. The body at this point possesses only potential energy.

Total energy at height, h is equal to potential energy.

Total energy at the top = Potential energy

Total energy at the top = mgh

Now when the body reaches the bottom of the building, it's height is zero.

h = 0

Potential energy = mgh

Potential energy = mg × 0

Potential energy = 0

Potential energy at the bottom is zero.

The total energy at the bottom of the building will be equal to kinetic energy.

Total energy at the bottom = Kinetic energy.

Total energy at the top = Total energy at the bottom.

Potential energy = Kinetic energy

mgh = Kinetic energy

$2 \times 9.8 \times h = 900 \\ \\ h = \frac{900}{2 \times 9.8} \\ \\ h = \frac{450}{9.8} \\ \\ h = \frac{450}{9.8} \times \frac{10}{10} \\ \\ h = \frac{450 \times 10}{9.8 \times 10} \\ \\ h = \frac{4500}{98} \\ \\ h = 45.918 \\ \\ h = 45.92 \: m$

ANSWER:

Height of the building , h = 45.92 m