A car starts from rest and travels for 7.5 s with a uniform acceleration of +2.8 m/s2. The driver then applies the brakes, causing a uniform acceleration of −2.5 m/s2.If the brakes are applied for 1.0 s, determine each of the following.
(a) How fast is the car going at the end of the braking period?
(b) How far has the car gone? m
First lets compute the distance from rest and before applying
the brakes and the velocity at the instant of applying the
where V=starting velocity
For the velocity at the instant of applying the brakes:
Then the driver applies the brakes for deceleration of 2.5 m/s^2 for 1 seconds
the final velocity will be
V(final)=v+AT , where A= deceleration of 2.5 m/s^2 and T= time of braking of 1 s
V(final)=21+(-2.5)(1) ---> A is negative because it is deceleration or acceleration at negative direction
The distance from the instant of braking to the final position will be:
Therefore the total distance is
total distance=98.5 meters
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