PHYS ce mc question(10)

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kwunkit

2010-04-14 3:42 am

a bicycle finishes a 100-meter journey in 9.77s.
assume that the bicycle starts from rest and moves with a uniform acceleration.
what is the acceleration of the bicycle throughtout the journey??
in my view
v=d/t
v=100/9.77
v=10.23541m/s
as it starts from rest and moves with a uniform acceleration
thus,the acceleration of the bicycle throughtout the journey is
a=(v-u)/t
a=(10.23541-0)/9.77
a=1.05m/s
WHAT WRONG ON THE ABOVE???

更新1:

THE CORRECT ANSWER IS 2.10 M/S

回答 (1)

天同

2010-04-14 4:06 am

✔ 最佳答案

The correct solution is as follows:
Use equation of motion: s = ut + (1/2)a.t^2
with u = 0 m/s, s = 100 m, t = 9.77 s, a = ?
hence, 100 = (1/2).a.(9.77)^2
solve for a gives a = 2.1 m/s2
Your solution is wrong because you have used the average volcity instead of the final velocity in the formula:

v=d/t
v=100/9.77 <--- average velocity = distance/time
v=10.23541m/s <---- this is the average velocity

a=(v-u)/t <---- v is the final velocity
a=(10.23541-0)/9.77
a=1.05m/s

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