Question

A brick of mass 5 kg is released from rest at a height of 3 m. How fast is it going when it hits the ground? Acceleration due to gravity is g = 9.8 m/s2.

A. 9.9 m/s

B. 8.1 m/s
C. 7.2 m/s
D. 7.7 m/s

Answer 1

the correct answer is D. 77 m/s

Answer 2

Speed of the ball when it hits the ground, v = 7.7 m/s

Step-by-step explanation:

It is given that,

Mass of the brick, m = 5 kg

It is released at a height of, s = 3 m

We need to find the speed with which it hits the ground. It can be calculated using the third equation of motion as :

`v^2-u^2=2as`

Here, a = g and u = 0

`v^2-u^2=2gs`

`v=√(2gs)`

`v=√(2* 9.8* 3)`

v = 7.668 m/s

or

v = 7.7 m/s

So, the velocity of the ball when it hits the ground is 7.7 m/s. Hence, this is the required solution.