Question

a resultant force of 40 Newton acts for a 4 second on a body of mass 2 kg initially at rest what is the momentum of the body at 4 second​

Answer 1

Given :

Force acting on the body ( F ) = 40 N .

Time during which the force acts ( t ) = 4 s .

Mass of the body ( m ) = 2 kg .

We know that the force of a body is the product of the mass of the body and the acceleration of the body .

F = m × a

⇒ a = F / m

⇒ a = 40 N / 2 kg

⇒ a = 20 N/kg

⇒ a = 20 m/s²

Acceleration of the body ( a ) = 20 m/s² .

By the Laws of Motion :

v = u + a t

⇒ v = 0 m/s + 20 m/s² × 4 s

⇒ v = 0 m/s + 80 m/s

⇒ v = 80 m/s

The final velocity ( v ) is 80 m/s .

Momentum at 4 s = mass × final velocity

⇒ Momentum = 2 kg × 80 m/s

⇒ Momentum = 160 kg m/s

The momentum will be 160 kg m/s after 4 seconds .

Answer 2

Answer:

160 kg m/s

Explanation:

Given that ;

Resultant force of body (F) = 40 N

Time taken by body (T) = 4 secs

Mass of body (M) = 2 kg

We know that;

The resultant force of the body is equal to the product of mass of the body and it's acceleration.

F = m × a

40 = 2 × a

a = 40 / 2

a = 20 m/s²

Hence, the acceleration of the body is 20 m/s².

Using first equation of motion :

v = u + at

v = 0 + 20 × 4

v = 20 × 4

v = 80 m/s

Thus, it's final velocity is 80 m/s.

Now, we need to find the momentum :-

We know that, momentum is the product if mass and it's velocity.

Momentum = Mass × Velocity

Momentum = 2kg × 80m/s

Momentum = 160 kg m/s.

Hence, the momentum of the body is 160 kg m/s.