A car is travelling at 10mps, when the driver stepped on the brake and stopped the car at a distance of 100meters. Is the time to stop the car equal to 15 secs ?
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Answer:
No, the time to stop the car is not 15sec its 20 sec.
Step-by-step explanation:
We are given that,
Initial velocity (u) = 10m/s ;
final velocity (v) = 0m/s (since the car stops)
Distance coverd (s) = 100m
To check whether time (t) = 15s ?
Using 3rd equation of motion
v²-u²= 2as we get a= v²-u²/2s
therefore a= 0²-(10)²/2×100= -100/200= -1/2m/s²
= -0.5m/s²
now using first equation of motion we get,
v=u + at which on rearranging gives us
t=v-u/a
therefore, t = 0-10/-0.5= 10/0.5 =20 sec
Hence the time to stop the car is 20 sec not 15 sec.
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