Practice-4 on Speed, Velocity, and Acceleration: Solution-4

Question 1: A ball is projected upward. Eventually, after the ball reaches its maximum height, it will fall back.
Indicate which statement is correct:
At the highest point in its motion, the ball's velocity is zero.

Question 2: Assume a student throws a ball vertically downward with a velocity of 10 m/s.
If air friction is considered negligable then calculate the speed of the ball one second later.
Answer: assuming that g = 9.8 m/s2 then speed of the ball 1 second later = 19.8 m/s

Question 3: Suppose you throw a ball vertically with a velocity of 10 m/s.
Approximately, when will it reach its highest height?
Answer: In 1 s. After 1 second, the gravity will push it down.

Question 4: Assume a television screen fall down from rest at a great height.
Calculate the speed after it has fallen for 5 seconds where air resistance is considered negligible.
Answer: 49 m/s
Explanation: acceleration (a) = speed (v) divided by elapased time (t), which implies that v = a × t = 9.8 m/s2 × 5 s = 49 m/s

Question 5: Assume a box of 5 kg is dropped from a building and hits the ground in 7 s.
Calculate the time it takes for a 10-kg box to hit the ground where air resistance is considered negligible.
Answer: 7 s

Explanation: since air resistance is zero then the time would stay the same.

Question 6: If a rocket is fired from a fighter jet and assuming that air resistance is negligible.
Which statement is correct about the rocket.
Answer: Its speed increases at 9.8 m/s.

Question 7: If you throw a ball up in the air.
Indicate the status of the ball when it reaches its highest point.
Answer: velocity is zero and the acceleration is downward.

Question 8: If you throw a ball up in the air with an initial velocity of 20m/s.
Calculate the ball's velocity after 4 seconds.
Answer: − 19.2 m/s

Explanation: 20 m/s - 4 s × 9.8 m/s2 = − 19.2 m/s

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Date of last modification: 2022