Question

start from rest, Rohan accelerates velocity to 12/s in 30 seconds then he applied brakes such that the velocity of car comes down to 8m/s in the next 5 s.calculate the acceleration in both the cases.

Answer 1

Hey Friend,

Question: 

Start from rest, Rohan accelerates velocity to 12/s in 30 seconds then he applied brakes such that the velocity of car comes down to 8m/s in the next 5 s.calculate the acceleration in both the cases.

Solution:

lets be familiar with the terms

Acceleration: It is basically rate of change of velocity of an object.

Velocity: it is basically rate of change of position of an object .

change in velocity: final velocity - initial velocity 

So now the formula for calculating the acceleration will be 

Acceleration=change in velocity/change in time 

Now coming to your question

In first case 
change in velocity is 12m/s
change in time is 30s

acceleration=12/30
                    =0.4m/s^2 

Second case:
change in velocity: 8-12=-4m/s
change in time:5s

Acceleration=-4/5
                  =-0.8m/s^2
 
Here the negative sign indicates that the acceleration is decreasing 

Take the absolute value for magnitude 

hope this helps you 

Please mark brainliest if you liked it 

Regards :)

Answer 2

Answer:

Acceleration =change in velocity /change in time

in first case

change in velocity in 12m/s

change in time is 30 s

acceleration =12/30

=0.4m/s^2

second case

change in velocity :8-12=4m/s

change in time :5s

Acceleration =4/5

=0.8m/s^2