1. A basketball player achieves a hang time of 0.827 s in dunking the ball. What

Question

1. A basketball player achieves a hang time of
0.827 s in dunking the ball.
What vertical height will he attain? The
acceleration of gravity is 9.8 m/s^2 .
Answer in units of m

2. A bullet is fired straight up from a gun with a
muzzle velocity of 136 m/s.
Neglecting air resistance, what will be its
displacement after 4.6 s? The acceleration of
gravity is 9.8 m/s2 .
Answer in units of m

3. Janet jumps off a high diving platform with
a horizontal velocity of 1.57 m/s and lands in
the water 2.9 s later.
How high is the platform? The acceleration
of gravity is 9.8 m/s2 .
Answer in units of m

Explanation / Answer

2. The bullet will lose 9.8 m/s of speed every second, therefore after 4.6 seconds it has lost 4.6 x 9.81 = 45.1 m/s leaving it with 136 – 45.1 = 90.9 m/s. Its average speed over the 4.6 seconds interval was therefore (136 + 90.9)/2 = 113.45 giving it a displacement of 113.45 x 4.6 = 521.9 m. 3. Janet's horizontal velocity is irrelevant. We do need to know her initial vertical velocity and assume here that this is 0. Janet's vertical speed when she hits the water = 9.8 x 2.9 = 28.42 m/s Janet's average speed during her fall is therefore (28.42 + 0)/2 = 14.21 m/s So the distance Janet falls = height of platform = 14.21 x 2.9 = 41.21 m

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