A small car has a mass of 300 kg and it is brought to rest in 4 seconds from a speed of 20 metres per second.If there is no resistance to motion,find the force exerted by the brakes
a = change in velocity/change in time
= -20/4 = -5 m/s^2
F = m a = -300*5 = -1,500 Newtons
V=0m/s,u=20m/s,t=5s find acceleration then the required force
To find the force exerted by the brakes, we can use Newton's second law of motion, which states that force (F) is equal to the mass (m) multiplied by the acceleration (a):
F = m * a
In this case, the car is being brought to rest, so its final velocity (vf) is 0 m/s, and the initial velocity (vi) is 20 m/s. The time taken to come to rest (t) is 4 seconds.
So, the acceleration (a) can be calculated using the following formula:
a = (vf - vi) / t
a = (0 - 20) / 4
a = -20 / 4
a = -5 m/s^2
The negative sign indicates that the car is decelerating.
Now we can substitute the mass and the acceleration into the force formula:
F = 300 kg * -5 m/s^2
F = -1500 N
The force exerted by the brakes is -1500 N, which means that the brakes are applying a force of 1500 N in the opposite direction of the car's motion to bring it to rest. The negative sign indicates that the force is in the opposite direction to the car's motion.