A disc at rest without slipping, rolls down a hill of height (3×9.8)m. What is its speed when it reaches at the bottom?

The speed as it reaches the bottom is  24m/s

Explanation:

Given parameters:

   Height of hill  = (3 x 9.8)m = 29.4m

Unknown:

Final speed as it reaches the bottom = ?

Solution:

 To solve this problem, we apply;

    v² = u² + 2gh

v is the final velocity

u is the initial velocity

g is the acceleration due to gravity = 9.8m/s²

h is the height

note, the initial speed of the body is 0;

Input the parameters and solve;

    v² = 0² + 2 x 9.8 x 29.4

   v² = 576.24

   v = √576.24  = 24m/s

The speed as it reaches the bottom is  24m/s