Question

A car of mass 1000kg moving with a speed of 90 km/ h to stop it in 5sec calculate the force applied by brakes and total work done

Answer 1

Explanation:

u=90km/hr

=25m/s

v=0m/s

t=5sec

a=v-u/t

=0-25/5

=-5m/s²

F=ma

=1000×-5

=-5000N

v²=u²+2as

0²=25²+2(-5)s

0=625-10s

-625/-10=s

s=62.5m

now,

W=F×S

=-5000×62.5

=-312500J

Answer 2

Answer:

Given mass of car =1000kg

u=speed=90km/hr=90×  

18

5

​  

m/sec

u=25m/sec

it have to stop in 5sec

then final velocity =0

⇒v=u+at

o=25+a×5

=a=−5m/sec  

2

 

then the force applied by break is ma

=1000X−(5m/sec  

2

)

=−5000M

force =5000N by break

distance travelled to stop the car after break is applied (s=distance)

v  

2

=u  

2

+2as

0=(25)  

2

−2×5×s

=s=  

10

(25)  

2

  =62.5m

work done by break =F×s

w=5000×62.5=312.5KJ

Explanation: