1) There is a long smooth slope and we release balls from the top of it every 1.
ID: 1274432 • Letter: 1
Question
1) There is a long smooth slope and we release balls from the top of it every 1.5 s. Suppose the acceleration of the ball is 4.0 m/s2 and every ball is numbered in the releasing order. (a) 9.1 s after the first ball is release, what is the distance between ball No. 1 and ball No. 6? m What is the distance between ball No. 2 and ball No. 7? (b) When ball No. 5 reached the speed of 15.0 m/s, what is the distance between ball No. 1 and ball No. 5? What is the distance between ball No. 2 and ball No. 5?
2)A rock is dropped into a deep hole and 1.6 s later the sound of striking the bottom is heard. If the speed of sound is 340 m/s, what is the depth of the hole?
3)A rock is dropped into a hole 11.80 m deep. How many seconds later will the sound of striking the bottome be heard? The speed of sound is 340 m/s
4)A person driving her car at 48 km/h approaches an intersection just as the traffic light turns yellow. The yellow light lasts only 2.0 s before turning to red, and she is 30 m away from the near side of the intersection (Fig. 2-29). The intersection is 15 m wide. Her car's maximum deceleration is -5.0 m/s2, whereas it can accelerate from 48km/h to 70 km/h in 6.6 s. Ignore the length of her car and her reaction time.
a) If she hits the brakes, how far will she travel before stopping?
b) If she hits the gas instead, how far will she travel before the light turns red?
5)A train is slowing down from 46 m/s to 12 m/s in 10 s. Assume constant acceleration.
How far did it travel in this time?
Explanation / Answer
2
let depth = d
1.6 = .5 x 9.81x(1.6-t)^2
where t = d/340
= 12.1 m
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