What is Torque ?

(L)

The rotational motion of an object about an axis caused by the forces perpendicular to the axis.

L (NM) = Force (N) x Distance (M)

NB. Distance = distance from Pivot point

In which direction does positive torque turn ?

Anticlockwise

In which direction does negative torque turn ?

Clockwise

What is Newton's First law ?

Objects in motion or at rest tend to remain as such unless acted on by an outside force.

What is Inertia ?

Resistance to motion

What is momentum ?

A vector quantity (M)

M is also a measure of the force needed to stop or change the direction of an object.

Describe Linear Momentum

Linear M is the tendancy of an object to maintain motion in a straight line.

What is an Impulse ?

(I)

A measure of the change of momentum of an object

What are the two different types of Collision ?

###
- Elastic
- Inelastic

Describe an Elastic Collision, and give an example.

Objects rebound off each other. There is conservation of momentum and KE.

E.g. 2 rubber balls collide

Describe an inelastic collision, and give an example

Objects stick together.

There is also conservation of momentum, but not of KE (which is lost as heat or sound, so total energy is conserved).

E.g. Two cars colliding

Describe the equation for the conservation of momentum in a collision

What do you need to know in order to solve problems involving Torque ?

**Translational Equilibrium:**

Σ upward force = Σ downward force

**Rotational Equilibrium:**

Σ positive torque = Σ negative torque

N.B. If you have two unknowns, take 1 to be the pivot point and it will be eliminated (=0) because torque at pivot point = 0.

What happens when a force acts on an object ?

The object undergoes either:

- Translational motion
- Rotational motion
- Complex motion (translational and rotational)