A person riding on his bike started his motion from rest and his rate of change of velocity is 3m/s^2. After 20 seconds he applied breaks and bike stops in next four seconds. Find out the total displacement of the bike if it travelled in a straight line?
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Answer:
initial velocity = 0
final velocity = v
acceleration = 3m/s²
time = 20s
v = u + at
=> v = 3×40
=> v = 120m/s
therefore, v²-u²= 2aS
=> S = 120²/6
=> S = 2400m
2nd case:-
initial velocity = 120m/s²
final velocity = 0
time = 4s
a = v-u/t
=> a = 120/4
=> a = 30m/s² ( since the bike is decelerating, the minus sign can be removed )
S = ut + ½ at²
= 120×4 + 30×16/2
= 480 + 240
= 720m
Total displacement = 2400+720
= 3120m
Hope it helped :)
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