ODU Flashcards
What does the gradient of a st graph give?
The velocity of the object
What does the gradient of a vt graph give?
The acceleration of the object
Resolving vector formulas
(Velocity / force)
F(h) = Fcosθ
F(v) = Fsinθ
Newtons 1st Law
An object will remain at rest or continue to move in a straight line at a constant speed unless acted upon by an unbalanced force
Newtons 2nd Law
An object will accelerate if acted upon by an unbalanced force
F=ma
Newtons 3rd Law
Every action force has an equal and opposite reaction force
If A exerts a force on B then B will exert an equal and opposite force on A
Why does acceleration of a rocket increase when it rises (thrust does not change)
Unbalanced force due to
-burnt fuel decreasing mass
-thinner air reducing friction
-g decreases so weight is less
Steps to calculate tension
•Acceleration of system (unbalanced force/total mass)
•Tension (second mass x a)
Component of weight
Down slope: F=mgsin θ
Perp to slope: F=mgcos θ
Law of conservation of energy
Energy cannot be created or destroyed, only converted from one type to another
Definition of power
The rate at which energy is converted
Conservation of momentum law
The total momentum before a collision is equal to the total momentum after a collision in the absence of external forces
When is a collision inelastic
A collision is inelastic when the kinetic energy before the collision is greater then the kinetic energy after the collision
Area under a force time graph gives…
Impulse
Explain how air bags/crumple zones/bike helmets work
•Ft=mv-mu
•need to decrease force
•can’t change the change in momentum
•have to increase t
•greater time = smaller force
•less injury/damage
Einstein’s postulates (for relativity)
The laws of physics are the same for all observers
The speed of light never changes
What happens to time?
What is t’?
Time dilates (gets longer)
Observed time
What happens to length?
What is l’?
Length contracts (gets shorter)
Observer length
Define Doppler shift
The Doppler effect is the change in observer frequency of a wave when a source of the observer is moving.
What do - and + mean in Doppler shift formula
- towards
+ away
What does hubbles law state
The further away a galaxy is, the faster it is moving away
What is dark energy
A force that opposes gravity and causes the expansion of the universe
Evidence of Big Bang
•Expanding universe
•Cosmic Microwave Background Radiation
•Abundance of light elements
What happens to
•the peak intensity wavelength &
•the energy/intensity
of an object when the temperature increases?
•peak intensity wavelength decreases
•intensity/energy increases
What is acceleration of an object in free fall
9.8ms
Explain how a student would determine whether a collision is elastic or inelastic
Calculate the total kinetic energy before and (total kinetic energy) after.
If Ek before is equal to Ek after the collision, is elastic.
