Question

A force of 2000N acts on a body of mass 400kg, causing its velocity to change from 5m/s to
8m/s. How long did it take for the velocity to increase? The same force acts on a body of mass
100kg for the same interval of time. The body is moving with a velocity of 10m/s. Find its final
velocity
down.​

Answer 1

Question :-

A force of 2000N acts on a body of mass 400kg, causing its velocity to change from 5m/s to 8m/s.

i) How long did it take for the velocity to increase?

ii) The same force acts on a body of mass 100kg for the same interval of time. The body is moving with a velocity of 10m/s. Find its final velocity

Answer :-

i) Given :-

• Force = 2000 N
• Mass = 400 kg
• Initial velocity = 5 m/s
• Final velocity = 8 m/s

To Find :-

• Time

Solution :-

We know that,

Force = Mass × Acceleration

Substituting the value -

➩ 2000 = 400a

➩ a = 2000 / 400

➩ a = 5

Acceleration = 5 m/s²

Now, we have -

• u = 5 m/s
• v = 8 m/s
• a = 5 m/s²

Substituting the value in 1st equation of motion -

➩ v = u + at

➩ 8 = 5 + 5t

➩ 5t = 8 - 5

➩ 5t = 3

➩ t = 3 / 5

➩ t = 0.6

Time = 0.6 sec

ii) Given :-

• Force = 2000 N
• Mass = 100 kg
• Initial velocity = 10 m/s
• Time = 0.6 sec

To Find :-

• Final velocity

Solution :-

Force = Mass × Acceleration

Substituting the value -

➩ 2000 = 100a

➩ a = 2000 / 100

➩ a = 20

Acceleration = 20 m/s²

Now, we have -

• u = 10 m/s
• t = 0.6 sec
• a = 20 m/s²

Substituting the value in 1st equation of motion :-

➩ v = u + at

➩ v = 10 + 0.6 × 20

➩ v = 10 + 12

➩ v = 22 m/s

Final velocity = 22 m/s