Forces Flashcards
What is a vector quantity?
A quantity that has a size and a direction e.g. force, velocity
What is a scalar quantity?
Quantities with size but no direction e.g. speed, distance
What is a contact force?
When two objects have to be touching for a force to act e.g. friction
What is a non contact force?
Where objects do not need to be touching for the force to act e.g. magnetic forces
How does gravity effect anything near a planet or star?
On the surface of the planet, it makes all things accelerate towards the ground it gives everything a weight
What is weight?
The force acting on an object due to gravity
What is a centre of mass?
Where the force is acting at a single point on the object; normally the centre
How do you find the weight of an object?
Mass x gravitational field strength
How is a free body diagram used?
The size of the arrows shows the relative magnitude of the forces and the direction show the direction of the force acting on the object
What is resultant force?
If there are more than one forces acting on an object (with the same effect) the overall effect on the object is called resultant force
What happens when a force moves an object?
Energy is transferred and work is done on the object
How can an object be elastically deformed?
If it can go back to its original shape and length when the force is removed
How can an object be inelastically deformed?
If it doesn’t return to the original shape and length after the force has been removed
How does an elastically deformed object affect the energy transferred?
When work is done on the object, energy is transferred to the elastic potential energy stored. If the object is elastically deformed, ALL of the energy goes to the elastic potential energy store
What is the relationship between extension and force?
They are directly proportional
Why does force and extension being directly proportional stop?
There is a limit to the amount of force you can apply to an object for the extension to keep on increasing proportionally; this is known as the limit of proportionality
What is pressure?
The force per unit area
What is density?
A measure of compactness of a substance
What happens when the depth of a liquid increases?
The number of particles above that point increases which means that the weight of these particles adds to the pressure felt at that point
What happens when an object is submerged in a fluid?
The pressure of the fluid exerts a force on it from every direction
What is the upthrust of an object submerged in water?
This is a resultant force upwards and is equal to the weight of the object submerged
What happens if an object floats?
This means that the weight of the object is the same as the upthrust
What does an object float upon depend on?
The density
What happens to an object that is less dense than the fluid it is placed in?
This means that it weighs less than the equivalent volume of fluid so it displaces a volume of fluid that is equal to its weight before it is completely submerged
What happens to an object that is denser than the fluid it is placed in?
It is unable to displace enough fluid to equal its weight, so its weight is always larger than the upthrust and it will sink
Why does atmospheric pressure decrease with height?
Atmospheric pressure is created on a surface by molecules colliding with that surface, so when altitude increases, the atmosphere gets less dense, so there are fewer air molecules that are able to collide with the surface