What is a force?
A force is a push or a pull.
What is mass?
How much stuff something is made of.
What is gravity?
The force that makes something fall to the ground.
What are kilograms (Kg)
The units of mass.
What is weight?
The pull of Earth’s gravity on something.
What increases friction?
Moving in liquid
What decreases friction?
Streamlined shape Smooth surface Moving slowly Small area Libration
What are tree things that forces do?
They push, pull or change the direction that objects re moving in, and change their shape.
What type of arrows show the direction and size of the force?
Force arrows show the direction and the size of the force.
What is contact force?
Contact force is when you are touching something.
What are tow types of contact forces?
Friction and air resistance are contact forces.
What are two types of non-contact forces?
Gravity and the force between magnets are both non-contact forces.
What happens to the tennis ball when gravity ‘acts’ on it?
The force of gravity acts on a tennis ball travelling through the air. The Earth pulls the ball down even though it is not touching it.
What are interaction pairs?
Interaction pairs are forces in pairs.
How do you measure forces?
You can measure force with a newton meter (sometimes called a spring balance). All forces are measured in newtons (N).
What happens when a ball hits the floor?
The ball deforms.
What can forces do to objects?
Forces can compress (squash) or stretch objects.
What happens when you exert force on an object?
When you exert force you can deform an object.
What two things can you do to an object?
You can compress an object or you can stretch an object.
What happens when you stand on the floor?
The floor pushes up on you when you stand on it.
What happens when you exert force on a solid object?
You compress the bonds when you exert force on an object.
What are the particles joined together by?
The particles are strongly joined together by bonds.
What happens when you stand on the floor?
Your weight pushes the particles together.
The bonds are compressed.
They push back and supports you.
What is a reaction force?
A support from a chair or the floor is called the reaction force.
What objects stretch when you exert force on them and what is the amount that they stretch is called?
Bungee cords, springs and even lift cables all stretch when you exert a force on them. The amount that they stretch is called the extension.
What is it called when the bungee cord has stretched as far as it will go?
Not only does the bungee cord pull her back up but also there is tension.
What a happens if you ‘double’ the force on a spring?
If you ‘double’ the force on a spring the extension will ‘double.’
What can you use to measure the size of the force exerted from the spring?
You can use the length of the spring to measure the size of the force.
What happens when you remove the force?
When you remove the force the spring goes back to its original length.
What does the elastic limit mean?
At some point the spring will not go back to its original length when you remove the force. This is called the elastic limit.
What type of springs are designed to never go past there elastic limit?
Trampoline springs are designed to never go past their elastic limit.
What happens to the shape of the bungee cord when you stretch it?
The shape of the bungee cord changes when you stretch the cord.
What is Hooke’s Law?
If the extension doubles when you double the force then the object obeys Hooke’s Law.
What does linear mean?
Liner means straight, it is normally used in graphs.
What can friction do?
Frictions grips objects.
How does friction help you to walk?
As the friction between your foot and the road produces the force to move you forward.
How do the brakes work in a car and on a bike?
The brakes on your bike and in a car work because of friction.
How can you reduce friction and what is it called?
One way to reduce friction is by using oil or grease. This is called lubrication.
What do snowboarders do to reduce friction?
Snowboarders wax their boards to reduce friction between the board and the snow.
What happens when you oil the chain of your bike?
The surfaces move sat each other more easily.
What will both a dolphin swimming and a surfer paddling through the water experience?
They will both experience water resistance.
What will a snowboarder experience when they jump through the air?
They will experience air resistance.
What are both water resistance and air resistance called?
The are both called drag forces.
What type of shape reduces drag forces?
A streamlined shape can reduce friction
What type of object exerts a magnetic force?
Magnets exert a magnetic force on magnetic materials or other magnets without touching them.
What is an electrostatic force?
An electrostatic force is when you rub a balloon you can pick pieces of paper with it.
What are magnetic and electrostatic forces called?
They are called non-contact forces.
What is force field in physics?
A region where something feels force.
What are balanced forces?
Forces acting on an object that are the same size but act in opposite directions.
What does equilibrium mean?
It means balanced.
When forces are the same size what happens?
They cancel out.
What happens if the forces are not the same size?
The forces don’t cancel out.
What are unbalanced forces?
Opposing forces on an object that are unequal.