The brakes of a care are applied to give it an acceleration of -3m/s^2. The car comes to a stop in 5 s. What was its speed when the brakes were applied?
Vf = Vo + at = 0,
Vo = -at = - (-3)*5 = 15m/s.
To find the speed of the car when the brakes were applied, we can use the equation of motion:
v = u + at
Where:
v = final velocity (0 m/s since the car comes to a stop)
u = initial velocity (the speed of the car when the brakes were applied)
a = acceleration (-3 m/s^2)
t = time taken to come to a stop (5 s)
Rearranging the equation, we have:
u = v - at
Substituting the given values, we get:
u = 0 - (-3 * 5)
u = 0 + 15
u = 15 m/s
Therefore, the speed of the car when the brakes were applied was 15 m/s.