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What is a machine?
A device that changes a force and makes work easier.
What are the two types of machines?
Simple and complex.
What is aerodynamics?
Aerodynamics is the way objects move through air.
What happens if a ship weighs less than the water it displaces?
The ship will float.
The energy to move a car, where can it come from?
It can come from electricity generated in an electric motor or from burning fossil fuels in a combustion engine.
What is a pulley used for?
A pulley is used to lift and pull heavy weight.
What is a wedge used for?
A wedge is used to separate two objects.
What is lift?
Lift is the push that lets a plane move upwards.
What happens if a ship weighs more than the water it displaces?
It will sink.
Why is the movement of a car along the road possible?
Because of a pair of action-reaction forces.
Levers, an inclined plane and a wheel and axle.
How is the point of support of a lever called?
The point of support of a lever is called fulcrum.
What is thrust?
Thrust is the force which pulls a plane forwards.
Why do ships float?
Because they are filled with air, which makes them lighter than the displaced water.
What is friction?
Friction is the resistance that the tyres on a car's wheels meet when they move on a road surface.
What is weight?
Weight is the force of gravity on the plane which pulls it towards the centre of the Earth.
What is drag?
Drag is the resistance that the air opposes to movement.
Lift must be greater than weight.
Thrust must be greater than drag.
What is Archimedes' principle?
It states that an object immersed in water experiences an upward force equal to the weight it displaces.
What does it mean that cars are aerodynamic?
It means that they are designed to minimise drag and allowing the cars to save fuel and move faster.
How are the wings of a plane? Why?
The wings of a plane are curved on top and flatter on the bottom so that the air flows faster over the wings and the plane is lifted up in the sky.
When a plane moves at a constant speed and in level flight, how are the four forces?
Drag = thrust
Lift = weight
The forces of a plane when it lands must be...
Lift must be less than weight.
Thrust must be less than drag.
What is special about cargo ships?
It has water tanks, which are used to change its weight so that it floats with and without cargo.
With no cargo = water tanks filled
With cargo = water tanks empty
What is grip?
Grip is the amount of traction the tyres have on the road.