Question

Define linear momentum of a body.

Answer 1

Linear momentum describes a relationship between the mass and velocity of an object, and we can see this when it is written in equation form, p = mv, where p is momentum, m is mass in kg and v is velocity in m/s.

Answer 2

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Linear Momentum is a vector quantity and is given by,

P(vector) = m×v(vector)

Where, m = mass of the body and v = velocity of the body.

Consider the two bodies at rest of same mass (let m) and are placed some distance apart (let r), then gravitational force acting between them is given by :—

F = (G×m×m)/r^2

This force provides acceleration to both bodies that makes them move towards each other with some velocity (let v).

Let us consider them to be on x —axis. So, body on right side starts moving towards origin and body on left starts moving away from origin. It means that both bodies moves in opposite direction.

Momentum of body on left is given by :—

P(1) = m×v (away from the origin)

Momentum of the body on right is given by :—

P(2) = m×v (towards the origin)

Since the magnitude of both momentum is same but direction is opposite, so according to vector law of addition the net momentum of the system still remains zero, as they cancel each other.

So even if a gravitational force acts between them they still have a final linear momentum zero.

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