1.A ball is thrown vertically downward with an initial speed of 15.8 m/s from a

Question

1.A ball is thrown vertically downward with an initial speed of 15.8 m/s from a building whose height is 122 m. How long does it take for the ball to strike the ground?

2.You are driving with a speed of 85 mile/hour in interstate 10 from Phoenix toward Los Angeles, when you see a large piece of debris 128m ahead on the highway. You push the brake pedal as hard as you can to try to avoid the collision. If the brake provides an acceleration of -8.50 m/s2,

How far will the car go before stopping?

Can you avoid hitting the debris?

3. A motorcycle is traveling at a speed of 6.22 m/s when it crosses a line 12.0 m from its starting point. The motorcycle continues going with an acceleration of 1.78 m/s2 until it crosses a mark 121 m from the starting point. How long does it take for the cycle to go from the 12.0-m mark to 121-m mark?

Explanation / Answer

1)

initial speed of the ball , u = 15.8 m/s

initial height , hi = 122 m

final height = 0

Using second equation of motion

y = u * t + 0.50 at^2 + hi

0 = 15.8 * t - 0.50 * 9.8 * t^2 + 122

solving for t

t = 6.86 s

the time taken is 6.86 s for the ball to reach ground

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