Question

calculate intial velocity if a body has retadation of 5m/sec square which finally comes to rest in 2 sec​

Answer 1

if body has velocity and acceleration in opposite direction then initial body will move in direction if velocity with decreasing speed and then come to rest and will start moving in direction of acceleration with increasing speed.

so initial velocity of body is 10m/s and acceleration of the object is −5m/s  

2

 

so time taken to stop once is 2 sec. using v=u+at

displacement at that time is 10m. using S=ut+  

2

1

​  

at  

2

 or by v  

2

−u  

2

=2as

after this the body will start moving in reverse direction so maximum displacement is 10m.

and distance covered in next 1 sec id calculate by S=ut+  

2

1

​  

at  

2

 

so D  

2

​  

=2.5m so total distance covered in first 3 sec is 10+2.5=12.5

so best possible answers are A,C.