Topic 5+6-Forces and Waves Flashcards
What are the two types of quantities?
- Scalar.
- Vector.
What quantity is force?
Vector.
What quantity is speed?
Scalar.
What is a scalar quantity?
Something that only has a magnitude but no direction.
What is a vector quantity?
Something that has a magnitude and a direction.
All forces are…
Contact or non-contact.
What is an interaction pair?
A pair of forces that are equal and opposite and act on two interacting objects.
What is the equation for weight?
mass x gravitational field strength.
Are mass and weight directly or indirectly proportional?
Directly proportional.
What do free body diagrams show?
All the forces acting on an object.
What is meant by the resultant force?
The overall force on a point or object.
What is the equation for work done?
Force x distance.
When is an object in equilibrium?
When all of the forces add together to equal zero.
What are objects that have been elastically deformed called?
Elastic objects.
What does it mean if an object has been elastically deformed?
It can go back to its original shape and length after a force has been removed.
What is the equation for force?
Spring constant x extension.
What is the equation for a moment of a force?
Force x distance.
What is the equation for pressure?
Force over area of surface.
What is meant by density?
How close the particles are together in a substance.
If the upthrust is equal to an objects weight…
The object will float.
What is atmospheric pressure caused by?
Air molecules colliding with the surface of the earth.
As the altitude increases what happens to the atmospheric pressure?
It decreases.
Why does the atmospheric pressure decrease with higher altitude?
Because less particles are able to collide with the surface of he earth.
What is the typical speed of a person walking? (idk why we need to know this but it says we do)
1.5 m/s
What is the typical speed of a car?
25 m/s
What is acceleration?
The change in speed over time.
What direction does friction always act?
In the opposite direction to movement.
What is drag?
The resistance you get in a fluid.
what counts as a fluid?
Liquid or gas.
What does newtons first law say?
That a resultant force is needed to make something start moving, speed up or slow down.
What is the equation for resultant force?
Acceleration x mass.
What does inertia mean?
The tendency for motion to remain unchanged.
What does newtons third law say?
When two objects interact, the forces they exert on each other are equal and opposite.
What is your thinking distance affected by?
- Your reaction time.
- Your speed.
What is meant by your thinking distance?
How far the car travels due to your reaction time.
What is meant by breaking distance?
How far the car travels under a breaking force.
What affects the breaking distance?
- Speed.
- Weather.
- Condition of your breaks.
What does braking rely on?
Friction between the brakes and the wheels.
What test can you use to test reaction times?
The ruler dropping test.
What affects your reaction time?
- Drugs.
- Tiredness.
What is the equation for momentum?
Mass x velocity.
What quantity is momentum?
Vector.
What is the idea that in a closed system the total momentum before an event is the same as after called?
The conservation of momentum.
What is the conservation of momentum?
The idea that in a closed system the total momentum before an event is the same as after the event.
What is meant by a closed system?
No forces are acting on it.
What causes momentum to change?
Force.
What direction do waves transfer their energy?
In the direction they are travelling.
What is meant by the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position.
What are the two types of waves?
- Transverse.
- Longitudinal.
What are the oscillations like in transverse waves?
Perpendicular to the direction of energy transfer.
What does oscillation mean?
Vibration.
what are the oscillations like in longitudinal waves?
Parallel to the direction of energy transfer.
What is the equation for wave speed?
Frequency x wavelength.
What can you use the measure the speed of sound?
An oscilloscope.
What is the speed of sound?
330m/s.
What happens when waves arrive at a boundary between two materials?
They can be absorbed, transmitted or reflected.
What does it mean when waves are transmitted?
They pass straight through.
What is the rule for when waves are reflected?
Angle of incidence = angle of reflection.
What is meant by the angle of incidence?
The angle between the incoming wave and the normal.
What is meant by the angle of reflection?
The angle between the reflected wave and the normal.
What can reflection be?
Specular or diffused.
When does specular reflection happen?
When a wave is reflected in a single direction by a smooth surface.
When does diffuse reflection happen?
When a wave is reflected by a rough surface.
Why does diffuse reflection happen?
The normal is different for each incoming ray.
What is meant by the normal?
The imaginary line that is perpendicular to the surface at the point of incidence.
What are radio waves made up of?
Oscillating charges.
What are EM waves made up of?
Oscillating charges.
The frequency of waves produced will be equal to…
The frequency of the alternating current.
What are radio waves mainly used for?
Communication.
What is meant by a perfect black body?
Best possible emitters of radiation.
