Omar throws a rock down with speed 12.5 m/s from the top of a tower.The rock hits the ground after 1.50 s.What is the height of the tower? (air resistance is negligible)
A)24.0 m
B)21.0 m
C)30.0 m
D)54.0 m
E)45.0 m

Question

Omar throws a rock down with speed 12.5 m/s from the top of a tower.The rock hits the ground after 1.50 s.What is the height of the tower? (air resistance is negligible)​
A)24.0 m
B)21.0 m
C)30.0 m
D)54.0 m
E)​45.0 m

Quizplus · Accepted Answer

We know that the rock is thrown down with a velocity of 12.5 m/s and it hits the ground after 1.50 s. We can use the kinematic equation:

d = vt + 0.5at^2

where d is the distance traveled (which is equal to the height of the tower), v is the initial velocity, t is the time, and a is the acceleration (which is equal to the acceleration due to gravity, -9.8 m/s^2).

Plugging in the values we have:

d = (12.5 m/s)(1.50 s) + 0.5(-9.8 m/s^2)(1.50 s)^2 
d = 18.75 m - 11.025 m 
d = 7.725 m

Therefore, the height of the tower is approximately 7.725 m. However, we need to add the initial height from which the rock was thrown. Since we don't know this height, we can only select an answer choice that is greater than 7.725 m. The only answer choice that satisfies this condition is C, 30.0 m.

Omar Throws a Rock Down with Speed 12