With what minimum speed must you toss a 170 g ball straight up to just touch the 15-m-high roof of the gymnasium if you release the ball 1.6 m above the ground? Solve this problem using energy.
Express your answer to two significant figures and include the appropriate units.
and
With what speed does the ball hit the ground?
Express your answer to two significant figures and include the appropriate units.
With what minimum speed must you toss a 170 g ball straight up to just touch the 15-m-high roof of the gymnasium if you release the ball?
2016-06-17 5:51 pm
回答 (1)
2016-06-17 6:00 pm
Take g = 9.81 m/s²
Take all upward quantities as positive.
If the ball just touch the roof.
distance, s = (15 - 1.6) m
acceleration, a = -9.81 m/s²
final speed, v = 0 m/s
initial speed, u = ? m/s
v² = u² + 2as
0² = u² + 2 × (-9.81) × (15 - 1.6)
u = √[2 × 9.81 × (15 - 1.6)] m/s
u = 16 m/s
The minimum speed to toss the ball = 16 m/s
Take all upward quantities as positive.
If the ball just touch the roof.
distance, s = (15 - 1.6) m
acceleration, a = -9.81 m/s²
final speed, v = 0 m/s
initial speed, u = ? m/s
v² = u² + 2as
0² = u² + 2 × (-9.81) × (15 - 1.6)
u = √[2 × 9.81 × (15 - 1.6)] m/s
u = 16 m/s
The minimum speed to toss the ball = 16 m/s
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