A car of mass 1000kg is moving with a certain speed when a constant breaking force of 1000 N acts on it for 5 seconds and the speed of car reduces to half its original speed. Find the further time required to stop the car if the same constant force acts.

Asked by mkp400 | 17th Dec, 2017, 12:26: PM

Expert Answer:

Retardation = Force/mass = 1000 N/ 1000 kg = 1 m/s2
 
in 5 seconds initial speed v0 reduces to (v0/2). then begin mathsize 12px style v subscript 0 over 2 equals v subscript 0 cross times 5 space minus space 1 half cross times 1 cross times 25 comma space t h i s space g i v e s space v subscript 0 equals space 25 over 11 end style
now the speed is (25/22) m/s. Required time to stop the car completely is given by
begin mathsize 12px style 0 space equals space 25 over 22 t space minus space 1 half cross times 1 cross times t squared space comma space t h i s space g i v e s space t space equals space 2 3 over 11 space s end style

Answered by  | 17th Dec, 2017, 01:32: PM