PHYSICS P5 - forces and motion Flashcards
What are scalar quantities?
Quantities that are described only by a magnitude.
What are vector quantities?
Quantities that are described by magnitude and direction.
What three things can a force change about an object?
Its speed, shape and direction
What are some examples of contact forces?
Friction
Air resistance
Tension
Upthrust
Reaction
What are some examples of non-contact forces?
Gravitational forces
Electrostatic forces
Magnetic forces
Weight
What are some examples of scalar quantities?
Mass
Distance
Speed
Energy
Time
Power
What are some examples of vector quantities?
Acceleration
Velocity
Force
What happens to forces in the same direction?
They are added together
What happens to forces in opposite directions?
They are subtracted, the smaller one from the bigger one.
What is Hooke’s law?
The extension of an object is directly proportional to the force applied.
If the spring is stiffer, what happens to the spring constant?
The spring constant is higher.
What is the spring constant of an elastic material?
The force per unit needed to stretch the elastic without inelastically deforming it.
What is meant by a moment?
A moment is a ‘turning effect’ of a force such as opening or closing a door.
What is the centre of mass of an object?
The point at which the mass of the object is thought of as concentrated.
What is the principle of moments?
In a balanced system, the anti-clockwise moment is equal to the clockwise moment.
What do levers do?
They increase the distance from the pivot at which the force is applied so less force is needed to get the same moment.
If the gears are the same size, what happens to the turning effect?
It remains constant
If the first gear is smaller than the second gear, what happens to the turning effect?
It’s greater
If the first gear is larger than the second gear, what happens to the turning effect?
It’s smaller
What are gears used for?
They are used for transmitting the rotational effect of a force from one part of machine to another.
What two things does pressure depend on?
- How much force is applied
- How big the area on which the force is applied is
What happens to pressure in fluids if you go deeper?
The pressure increases with depth because the water at the bottom of this container is pushed on by the weight of the water further up which causes it to be under higher pressure.
What are the steps for the required practical involving Hooke’s law?
- Set up equipment and measure the length of the spring with no masses and record it.
- Add mass (1n) and record length of the spring.
- Repeat by adding 1 newton of force every time
- Plot a graph
What is inelastic deformation?
The object won’t return to its original shape or length when the force is removed.
