Force and Motion

What is the difference?

Motion• Motion is the same as movement• It comes in 4 types:

-Rectilinear Motion (Straight Line)-Alternating Motion (Back and Forth)-Circular Motion (Round and Round)-Oscillatory Motion (Wobbling)

Understanding the types of motion

• It can be helpful to think of exercises for each type of motion: -running for rectilinear

-push ups for alternating

-arm rotations for circular

-jumping jacks for oscillating

What kind of motion do you think is represented by the pictures?

1. Oscillation

2. Rectilinear

3. Circular

4. Alternating

What is Force?

• Force is any action capable of producing motion

• An action doesn’t need to produce motion to be a force, it just has to be capable of it.Ex. With your hand push up on the underside of your desk. Does it move?Now hold your other hand out and try pushing up on it. Does your hand move?

Types of Forces (Gravity)

• What would happen if you jumped off a cliff?• Gravity makes you fall down of course!

• In this example the air drag is also a force because it changes the motion caused by gravity.

Normal Force

• So if gravity is always pulling down, why don’t we fall to the centre of the Earth?

• Because the ground keeps us up!• The force of the ground

keeping us up to cancel the force of gravity is called a normal force.

Applied Force

• The example where we pushed on our desks is called an applied force. This is the kind of force we use when we do pretty much anything (walking, lifting, moving our bodies).

Centripetal Force• Anytime something is moving in

a circle, it wants to fly away. (Think of what would happen if the guy in the picture let go of his chain.)

• This also explains why you don’t have to worry about flying out of a roller coaster doing a loop-de-loop.

• The centripetal force always points to the circle’s centre.

Air Resistance and Friction Forces

• There are certain forces which don’t make motion on their own but work against other forces.

• Air resistance force comes from needing to push all the air aside when we move. (Think of how much more difficult it is to walk through water.)

• Friction force comes from resistance when things rub together.

Tension Force

• Tension is the force that travels along a string or cable when it is pulling on something.

• Tension pulls on both ends of the string with equal force.

• In a tug of war,there is tensionin the rope equal to how hard the teamsare pulling.

Spring Force (last one!)

• Spring force is the force we feel when something is bent out of shape.

• When a spring is compressed or an elastic band is stretched, it wants to return to its original shape. This ability is the spring force.

What kind of Force is represented by the following pictures?