Section 1: forces and motion c) forces, movement and shape

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Kilogram (kg)

Metre (m)

Metre/second (m/s)

Metre/second2 (m/s2)

Newton (N)

Second (S)

Kilogram metre/second (Kg m/s)

Newton per kilogram (N\kg)

Units(1.1):

1.9 describe the effects of forces between bodies such as changes in speed, shape or direction Changes in speed

When an object is stationary it has an equal force pushing down and up. The downward force being gravity and the upward force being the surface the object is on. The object is not floating but it is not going into the ground.

When an object is accelerating it has the upwards and downwards forces but it also has forwards and backwards forces (drag and friction). The forward force is larger than the backward force when an object is accelerating.

When an object is going at a constant speed it has downward and upward forces as well as forward and backward forces. The forward and backward forces are equal, so the speed doesn't change even though the object is moving.

When an object is decelerating it has the equal upward and downward forces as well as forward and backward forces, but the backward force is larger than the forward one, slowing the object down.

Changes in shape

changes in shape affect momentum. Force= change in momentum/ time taken. An example of this is crumple zones in car decrease the force on the passengers.

Changes in direction

Which ever direction the force is greatest in will be the direction the object travels in.

Forces:

electrostatic

push

pull

friction

magnetic- two magnets placed near each other

upthrust- cork placed in water

Air resistance- feather dropped from a height, weight ar slowing it.

elastic

Gravity; acting downwards

Up thrust; acting upwards

Drag; acting against the movement

A force is a push or pull. A force can cause an object to accelerate or change shape.

Force is measured in Newton's(N) with a newton meter.

There are many types or force. Contact force occurs when two bodies touch each other.

Friction is a force vector quantity, it has magnitude and direction.

Vectors: has size and dircetion

Force

Displacement

Velociy

Scalars: has size no direction

Speed

Mass

Energy

Distance

1.12 understand that force is a vector quantity Force has magnitude, it is measured in newtons but it acts in a direction.

For example 3N drag

is an amount of force acting backwards.

1.13 find the resultant force of forces that act along a line Resultant force is the overall force acting in a direction on an object. It is best explained by digrams which show that the resulatnt force is the overall force given individual forces acting along a line.

Balanced and unbalanced forces: resultant force

Balanced forces:

Resultant force= 0

Object stays at rest, or continuous at the same speed in the same direction.

Unbalanced forces:

The object speeds up or slows down in the resultant force.

newton's second law of motion:

Force = mass x alcceleration

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