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Question
A speeding car changes its velocity from 108 kmh−1 to 36 kmh−1 in 4 s. Calculate its deceleration in
- ms−2
- kmh−2.
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Solution
Initial velocity = u = 108 kmh−1
u = `108xx5/18` m−1
u = 30 ms−1
Final velocity = v = 36 kmh−1
v = `36xx5/18` ms−1
v = 10 ms−1
Time = t = 4 S
Deceleration = a = `("v"-"u")/"t"`
a = `(10-30)/4`
a = `-20/4` = −5 ms−2
a = `(-5xx3600xx3600)/1000` kmh−2 = −64800 kmh−2
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