Physics Motion

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[匿名]

2008-12-15 12:15 am

A ball is moving eastwards with an initial velocity of 10m/s.If the acceleration is 5m/s2 westwards, find its displacement after 2 and 6 second.

更新1:

In an emergency, a van travelling at 25 m/s has to stop in 30m the driver's reaction time is 0.4 and the thinking distance is 10m what is the average deceleration of van?

更新2:

question 2.

回答 (1)

Uncle Michael

2008-12-15 12:31 am

✔ 最佳答案

Take eastwards to be positive.

After 2 s:
t = 2s, u = 10 m/s, a = -5 m/s2
s = ut + (1/2)at2
s = 10(2) + (1/2)(-5)(2)2
s = 10 m
Displacement is 10 m eastwards.

After 6 s:
t = 6s, u = 10 m/s, a = -5 m/s2
s = ut + (1/2)at2
s = 10(6) + (1/2)(-5)(6)2
s = -30 m
Displacement is 30 m westwards.
=

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