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A ball is dropped from rest from a tower and strikes the ground 125 m below. Approximately how many seconds does it take the ball to strike the ground after being dropped? Neglect air resistance.

a. 2.5 s
b. 5 s
c. 7.5 s
d. 10 s

1 Answer

2 votes

Final answer:

The ball dropped from a tower 125 meters high would take approximately 5 seconds to reach the ground, given that there is no air resistance.

Step-by-step explanation:

To determine how long it takes for the ball to strike the ground after being dropped from a tower 125 meters high, we can use the kinematic equation for motion under constant acceleration due to gravity neglecting air resistance:

s = ut + 0.5at2

where:
s = displacement (125 m)
u = initial velocity (0 m/s, since the ball is dropped from rest)
a = acceleration due to gravity (9.8 m/s2)
t = time in seconds

We have s = 125 m, u = 0 m/s, and a = 9.8 m/s2. Substituting these into the equation, we can solve for time t:

125 = 0 + 0.5 × 9.8 × t2
125 = 4.9t2
t2 = 125 / 4.9

t2 = 25.51

t = √25.51

t ≈ 5 seconds

Therefore, the correct answer is approximately 5 seconds (Option b).

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