# Linear Momentum - Checking quick questions

• future_vet
In summary, the SI unit of momentum is N x s. In an inelastic collision where momentum is conserved, kinetic energy is lost. The momentum of a projectile is constant due to Newton's first law. The impulse imparted by a 4.0 N force acting for 3.0 s and then suddenly increasing to 15 N for one more second is 16.3 N·s.

#### future_vet

What is the SI unit of momentum? --> N x s

When a light beach ball rolling with a speed of 6.0 m/s collides with a heavy exercise ball at rest, the beach ball's speed after the collision will be, approximately? --> 6.0 m/s

In an inelastic collision, if momentum is conserved, then which of the following statements is true about kinetic energy? --> Kinetic energy is lost.

Which of the following is an accurate statement?
The momentum of a projectile is constant. <---
The momentum of a moving object is constant.
If an object is acted on by a non-zero net external force, its momentum will not remain constant.
If the kinetic energy of an object is doubled, its momentum will also be doubled.

A 4.0 N force acts for 3.0 s on an object. The force suddenly increases to 15N and acts for one more second. What impulse was imparted by these forces on the object? --> 16.3 N·s

Thanks!

I can't figure out how to find the impulse without mass...

Last edited:
1 and 2 are correct.

For #3, the answer is a bit ambiguous. All KE need not be lost.

#4 - Wrong. Hint: Newton's 1st law.

#5 - How did you get 19? What's the definition of impulse?

For #3:
If an object is acted on by a non-zero net external force, its momentum will not remain constant.
This seems to comply with the 1st law.

Impulse is what changes the momentum of an object.. right?

Thanks!

future_vet said:
For #3:
If an object is acted on by a non-zero net external force, its momentum will not remain constant.
This seems to comply with the 1st law.
Right. So is a projectile free of non-zero net external forces?

future_vet said:
Impulse is what changes the momentum of an object.. right?
Well, not exactly. Force is what changes momentum. Impulse is change in momentum(in a certain time interval).

$$J = F\Delta t = \Delta p$$, for a constant force F. J is impulse, btw.

future_vet said:

Thanks!

Now you tell me! :grumpy:

i just can't comprehend getting the impulse without mass.

## What is linear momentum?

Linear momentum is a physical quantity that describes the motion of an object. It is defined as the product of an object's mass and its velocity. In other words, it is the measure of an object's motion in a straight line.

## How is linear momentum calculated?

Linear momentum is calculated by multiplying an object's mass by its velocity. The formula for linear momentum is p = m * v, where p is the linear momentum, m is the mass of the object, and v is the velocity.

## What are the units of linear momentum?

The units of linear momentum are kg*m/s (kilogram meters per second) in the SI (International System of Units) system. In other systems, it can be expressed as g*cm/s (gram centimeters per second) or lb*ft/s (pound feet per second).

## What is the principle of conservation of linear momentum?

The principle of conservation of linear momentum states that the total linear momentum of a closed system remains constant. This means that in a closed system, the total amount of linear momentum before and after a collision or interaction is equal.

## How is linear momentum related to force?

According to Newton's second law of motion, the rate of change of an object's momentum is equal to the net force acting on the object. In other words, force is directly proportional to the change in an object's momentum over time.