Show the steps very clearly.
1. A car starts from rests and moves with a uniform acceleration of 1ms^-2 along a straight line.
(a) How fast will it be moving when it is 50m from its starting point?
2. A car gradually slows down steadily from 35m/s to 20m/s over a distance of 206m.
(a) Find the acceleration of the car.
(b) Find the time taken for it to slow down.
Two questions
2007-09-26 12:17 am
回答 (2)
2007-09-26 12:27 am
✔ 最佳答案
1) Apply v² - u² = 2ax, u = initial velocity = 0, a = 1ms-2, v² - 0² = 2 (1)(50)
v² = 100
v = 10 ms-1
The car will be moving at 10m/s when it is 50m from the starting point
2 (a) Apply v² - u² = 2ax, v = final velocity = 35m/s, u = initial velocity = 20m/s, x = displacement traveled = 206m,
(20)² - (35)² = 2a(206)
400 - 1225 = 412 a
a = -2.0 m/s²
The car decelerates at 2.0 m/s²
2(b) Apply v = u + at
20 = 35 + (-2)(t)
t = 7.5s
The car takes 7.5 seconds to slow down
2007-09-26 12:31 am
1a, since v^2-u^2 = 2as
v^2+0^2 = 2(1)50
v^2 = 100
v = 10ms^-1
2a, since v^2-u^2 = 2as
20^2-35^2 = 2a(206)
400-1225 = 412a
a = -2.00ms^-2(corr.to 3sig.)
2b, since v = u+at
20 = 35+(-2)t
-15 = (-2)t
t = 7.5s
v^2+0^2 = 2(1)50
v^2 = 100
v = 10ms^-1
2a, since v^2-u^2 = 2as
20^2-35^2 = 2a(206)
400-1225 = 412a
a = -2.00ms^-2(corr.to 3sig.)
2b, since v = u+at
20 = 35+(-2)t
-15 = (-2)t
t = 7.5s
參考: My Physics Knowledge
收錄日期: 2021-05-03 06:02:32
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