Forces

Force

Pull, pull or twist that acts on an object causing it to change direction

Contact force

Something has to be physically touching the object to apply a force.

1. Friction, tension, normal contact force

Non contact force

No need to physically be touching the objects to apply a force

1. Air resistance, gravitational force, magnetic force

Scalar

Quantity that only and a magnitude

Vector

Quantity that has a magnitude and a direction

Resultant forces

Total sum of all forces. Left force is negative when adding them up

Weight

Force that gravity pulls an object down with

Mass

Measure of how much matter there is in an object

Spring required practical

1. Set up your equipment

2. Add masses onto the spring - 100g or N each

3. Measure the extension of the spring with a ruler at each weight until the spring has elastically deformed

Moment

Turning force, force and distance form the pivot are perpendicular to each other.

Levers

Transmits the turning effect of a force. They can act in different or same directions

1. Able to get a large output force with a small input force.

Gears

Transmits a turning effect.

• small gear turns anticlockwise and big gear turns clockwise

• Turning effect in the bigger gear is 2x more as on the small gear

• The small gear rotates 2x more than the bigger gear

Momentum

How hard it is for an object to stop

Collision

In any collision, momentum is always conserved. Longer time in which momentum is lost or gained, the lower the force is

Benefits of momentum

Increases the collision time and reduces the force

Forces and terminal velocity

Falling objects have terminal velocity

Velocity remains constant and the object is no longer accelerating or decelerating

Sky diving

1. The objects weight will start pushing them down

2. Velocity increase = pushing force upwards

3. Rate of accelerating will decrease and resultant force will be smaller.

4. Velocity increases = air resistance increases to the same as the weight

5. Terminal velocity happens and the resultant force is now 0

Opening up a parachute

Air resistance increase because of the increase in SA

resultant force is upwards as it is accelerating upwards

When they slow down resultant force will be smaller = lower air resistance

Air resistance becomes equal to the weight 0. Terminal velocity

Centre of mass

Single point where all the objects mass seems to be acting from

Finding the centre of mass of an irregular object RP

1. Set up your equipment

2. Hang up the irregular object

3. Suspend the plumb line from the same point

4. Mark position of the thread

5. Rear the experiment on different sides of the irregular object, suspend from two other places

6. Mark the position of the thread

7. Where all this point meet is the centre of mass