JC Science - Forces

Force

Anything that causes an object to move or change velocity

What unit are forces measured in?

Newtons (N)

A force causes objects to:

-Accelerate / decelerate
-Change speed
-Change direction
-Change shape

Different forces

-Magnetic
-Gravity
-Driving
-Upthrust
-Reaction
-Elastic
-Water resistant
-Friction

Magnetic force

Force created when 2 opposite forces repel each other

Gravity (weight)

Downward force created by the mass of an object towards earth

Driving force

Forward force created by the engine of a moving object

Upthrust

Upwards force in water to stop objects sinking

Reaction

Force acting in the opposite direction

Elastic / tension

Force that stretches something

Water resistant

Force created due to the movement of water

Air resistance

Force created due to the movement of air

Friction

-Force created when 2 surfaces rub together + create heat
-Prevents easy movement between 2 objects

Friction advantages

-Grip between tyres + road
-Brakes use friction to stop
-Creates heat

Friction disadvantages

-Moving parts in engine wear away
-Rope / carpet burn
-Friction with air slows down vehicles reducing efficiency

Friction is affected by

-Downward force
-Roughness of the surface

Lubricant

Can be used to fill gaps or grooves to reduce friction

Newtons first law

Unless a force acts on it, an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction

Balanced forces

Causes objects to stay constent

Unbalanced forces

Causes objects to change speeds

Newtons second law

When a force acts on mass, it accelerates. The greater the force, the greater the acceleration

Force equation

mass x acceleration

Force triangle

Mass

How much matter something contains (kilogram)

Weight

The force of gravity on an object (Newtons)

Acceleration due to gravity (earth + moon)

Earth: 10m/s2
Moon: 1.6 m/s2

Newton's thrid law

For every action there is an equal and opposite reaction

Types of graphs

-Directly proportional
-Proportional
-Inversely proportional

Directly proportional graph

Proportional graph

Inversely proportional graph

Outlier

A value much greater or much less than the others in a data set

Dependent variable

What is measured

Independent variable

What is changed

Control variable

What is kept the same

Practical: Investigating friciton

1. Pull the block of wood across a surface
2. Use the spring balance + record the force required to move it
3. Repeat 2 times
4. Change surface + repeat the process