Question

2. A force of 5 N changes the velocity of a body fro
10 m/s to 20 m/s in 6 s. The force required to bri
the same change in 1.5 s is
(1) 10 N
(2) 15 N.
(3) 18 N
(4) 20 N​

Answer 1

Given :-

Force = 5 N

Initial velocity = 10 m/s

Final velocity = 20 m/s

Time = 6 sec

Time = 1.5 s

To Find :-

Force required

Solution :-

At first we need to find acceleration

We know that

v = u + at

20 = 10 + a(6)

20 - 10 = 6a

10 = 6a

10/6 = a

1.6 = a

Now,

Finding mass

F = ma

m = F/a

m = 5/1.6

m = 3.125 kg

Now

Finding acceleration for 1.5 sec

a = v - u/t

a = 20 - 10/1.5

a = 10/1.5

a = 6.66 m/s

F = ma

F = (3.125)(6.66)

F = 14.16 N = 15 N[approx]