Question

a body starts from rest with an acceleration 2m/s2 till it attains the maximum velocity then retards to rest with 3m/s2. if total time taken is 10 second then maximum speed attained is
a) 12m/s b) 8m/s
c) 6m/s d) 4m/s

Answer 1

a) 12 m/s.
the maximum speed attained will be 12m/s .

drawing the velocity-time graph will be helpful

a triangle will be formed

drop a perpendicular from the upper vertex to x-axis

now two triangles will be formed

since we know that the slope of v-t graph gives acceleration

apply tanΘ and get the answer

Answer 2

Given:

Acceleration a=2 m/sec²

Velocity v= 3 m/sec

Time taken in second t'=10 sec

To find:

Maximum speed attained to be

Solution:

First find the maximum velocity

V= u+at'

Putting above values

V= 2t'     as u=0

Now find the V(f)

V(f)= V - 3(10-t')

As the body came to rest V(f)=0

0=V- 3(10-t')

V=3(10-t')

Putting above value

2t'=30-3t'

5t'=30

t'=6 sec

Time taken is 6 sec. So, option C is correct.