A car of mass 200 kg is moving with a velocity of 25 m/s. Brakes are applied and the car comes to rest in 5 s. Find (i) the retardation (ii) the magnitude of force used to stop the car.
Answers
Answer:The final velocity of the car will be zero as it finally comes to rest after application of brakes. Since acceleration of the car is -5m/s²,thus the retardation of the car is 5m/s².
Explanation:
Given:-
→Mass of the car=200kg
→Initial velocity of the car=25m/s
→Time taken to come to rest=5s
To find:-
→The retardation
→Magnitude of force used to stop the car
Solution:-
The final velocity of the car will be zero as it finally comes to rest after application of brakes.
By using the 1st equation of motion,we get:-
=>v=u+at
=>a=v-u/t
=>a=0-25/5
=>a= -5m/s²
Since acceleration of the car is -5m/s²,thus the retardation of the car is 5m/s².
Now,by using Newton's 2nd law of motion,we get:-
=>F=ma
=>F=200(-5)
=>F= -1000N
Thus:-
→Retardation of the car is 5m/s².
→Magnitude of force is -1000N,or a
retarding force of 1000N