# Physics - Recall for Chapter 7; Laws of Motion and Momentum

## Recall Questions

State Newton’s first law?

The velocity of an object will only change if a resultant force acts on it.

State the ways in which an object’s velocity might change?

An objet may accelerate, decelerate, or change direction.

State Newton’s third law (long)?

When two objects interact, they exert forces on each other that are equal in magnitude, opposite in direction and of the same type.

State the four features of a Newton’s third law pair of forces?

- Equal magnitude.
- Opposite directions.
- Same type.
- On different objects.

State and explain whether momentum is a scalar or vector quantity?

Vector, as momentum is the product of mass and velocity, and velocity is a vector.

State the SI unit of momentum?

State the principle of conservation of momentum (long)?

In a closed system, where no external forces act, the total initial momentum is equal to the total final momentum.

What is an elastic collision?

A collision in which kinetic energy and momentum are both conserved.

What is an inelastic collision?

A collision in which kinetic energy is not conserved, but momentum and total energy are still conserved.

State Newton’s second law?

The resultant force acting on an object is equal to the rate of change of momentum of the object.

State the special form of Newton’s second law used when mass is constant?

Define the impulse of a force?

The product of the magnitutde of the force and the time it acts for.

What is the equation for the impulse of a force?

What does impulse represent?

The change in momentum.

What does the area under a force-time graph represent?

Impulse/change in momentum.

How can the conservation of momentum be applied to collusions in two dimensions?

Momentum in the $x$ and $y$ directions are conserved seperately.

What happens to objects that collide perfectly inelastically?

They stick together.