A2.5-kg brick falls to the ground from a 3-m-high roof. what is the approximate kinetic energy of the brick just before it touches the ground?

A 2.5-kg brick falls to the ground from a 3-m-high roof. What is the approximate kinetic energy of the brick just before it touches the ground?

a) 75J

b) 12J

c) 38J

d) 11J

Kinetic Energy of the brick just before it touches ground = 73.5 Joules, so according to the question, approximately correct options is 75 Joules.

Mass of brick = m = 2.5 kg

Height of roof = 3 m

Let us assume that the final velocity of the brick just before it touches the ground is v.

Kinetic energy of a body is given by: KE =

We need to calculate v before calculating KE.

By the Equation , where u is initial velocity, v is final velocity, a is acceleration, and s is distance traveled, we can calculate the required variable.

In this case, s = Height of roof, u = 0 because the brick is not thrown, but just falls, and a = gravitational acceleration = g = 9.8 .

So = 58.8

So = 7.66

So now we can calculate Kinetic Energy = = = 73.5

Also we need to convert KE into Joules.

1 = 1 Joule

So Kinetic Energy = 73.5 Joules.