What is a force?
A push or a pull
What unit are forces measured in?
What piece of equipment measured forces?
How can forces affect the movement of an object?
(i) Change it’s speed (faster/slower)
(ii) Stop it moving
(iii) Change it’s direction
(iv) Change it’s shape
How can forces be represented on a diagram?
Forces can be represented by arrows in a certain direction.
The size of the force must be labelled.
What is a contact force?
A contact force is a push or a pull on one object by another object that is touching it.
What is a non-contact force?
A force that pushes or pulls on an object without touching it is called a non-contact force
Give an example of a non-contact force?
- Gravitational force
- Magnetic force
- forces due to static electricity
Do forces act alone or in pairs?
Forces always act in pairs. These pairs are called interaction pairs.
What is weight?
Theweightof an object is defined as theforceof gravity on the object.
What is drag force/air resistance?
It is the force that acts on objects as move/fall through the air.
How does drag/air resistance affect the speed of a moving object?
It slows it down.
What type of shape can decrease the effect of air resistance.
A stream-lined shape
What type of force is thrust?
This can be any driving force, it may be a push or pull, but it could be an engine which forces an object forward.
What type of force is lift?
This is the force required to raise an object through a fluid. e.g. the force pulling an airplane upwards is lift.
What is friction?
It is a force that acts on objects when they are in contact with a surface, such as the ground. It slows objects down.
How can the force of friction be reduced?
Lubrication e.g. adding oil to the engine of a car.
What is gravity?
This pulling force affects every object on Earth. It is a force which pulls everything to the centre of the earth.
What is upthrust?
This is an upward force which acts in water, it acts on a object against gravity, and is why certain objects float.
What is tension?
Tension is a pulling force as tension can only pull an object. e.g. there is a tension force on the lead when walking a dog.
If the forces on an object are BALANCED (or if there are no forces acting on it), what happens to the object?
- a stationary object stays still.
- a moving object continues to move at the same speed and in the same direction.
When are forces UNBALANCED?
When two forces acting on an object are not equal in size, we say that they are unbalanced forces.
When forces are unbalanced it can cause an object to…
- Change it’s speed
What is the difference between weight and mass
- The weight of an object is the force of gravity on the object. Weight is measured in Newtons.
- Mass is a measurement of how much of something there is. Mass is measured in grams and kilograms.
What does Hooke’s Law state?
Hooke’s Law states: “If you double the force applied to a spring then the extension of the spring will double”.
What is elastic limit
This is the point of a spring/elastic beyond which it will deform and not return to it’s original shape.