Question

You are standing at the top of a high cliff. You drop a rock and it hits the ground 4 seconds later. How fast was it going when it hits the ground?

A. -9.8 m/s
B. -38.2 m/s
C. -29.4 m/s
D. -19.6 m/s

Answer 1

Answer:

B. -38.2 m/s

Explanation:

Given parameters:

Time of fall  = 4s

Unknown:

Final velocity of the rock  = ?

Solution:

To solve this problem, we use the expression below;

       V = U + gt

V is the final velocity

U is the initial velocity

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

t is the time taken

Now, insert the parameters and solve;

   V  = 0 + (9.8 x 4) = 39.2m/s