Term

Definition
When two things collide, the effect they have on each other depends on thier mass and initial velocity 


Term

Definition
Sir Isaac Newton realised that a force is needed to change the velocity of an object 


Term

Definition
Depends on the amount of force and the objects mass 


Term

Definition
Of a moving object;
= Mass x Velocity
p = mv 


Term
FORCE NEEDED TO GIVE AN OBJECT A CERTAIN ACCELERATION 

Definition
Force = mass x acceleration
F = ma 


Term
WHERE DOES NEWTONS LAW OF MOTION NOT APPLY? 

Definition
Inside an atom (quantum physics), Speeds approaching the speed of light or in strong gravitational fields (Einstiens theory of relativity) 


Term

Definition
Unit is kgms^{1}
Vector quantity  direction is same as the velocity



Term
NEWTONS FIRST LAW OF MOTION 

Definition
An object remains at rest or in uniform motion unless acted on by a force
(so basically a force is needed to change the motion of an object) 


Term

Definition
This means there is no resultant force acting on it
If the mass remains constant and the object has a constant momentum, the velocity will be constant; if the object lost/gained mass whilst moivng, velocity would change to keep momentum constant 


Term
NEWTONS SECOND LAW OF MOTION 

Definition
The rate of change of momentum of an object is proportional to the resultant force on it. The resultant force is proportional to the change of momentum per second 


Term

Definition
An object of mass m is acted by a constant force of F.
Initial momentum = mu , Final momentum = mv
Force is proportional to change of momentum per second.
F≈mvmu/t
F≈ m(vu)/t
a = vu/t
F ≈ ma
F = kma
K = constant of proportionality = 1 


Term

Definition
This form of Newtons second law is used when there is a continuous loss or gain of mass of an object 


Term

Definition
The impulse of a force is the the force x the time for which the force acts.
Impulse = Ft
Ft = ♦(mv)
This unit is usually Ns^{1} 


Term

Definition
Rearranging Newtons second law gives:
F = mv  mu/t
The area under a force  time graph gives the change of momentum or impulse of the force 


Term
IMPACT FORCES  STATIONARY 

Definition
If something is initially stationary and the impact causes it to accelerate to v , the gain of momentum will be mv so the force of the impact will be F = change in momentum / contact time = F = mv / t 


Term
IMPACT FORCES  CHANGING VELOCITY 

Definition
If object is moving with velocity u and the impact changes it's velocity to v the change in momentum of the ball is mvmu so impact force =
F = change of momentum/contact time = mvmu/t 


Term

Definition
Crumple zones, seatbelts, and airbags are all designed to lessen the impact force on people. This happens by increasing the time which decreases the acceleration/deceleration which lowers the impact force 


Term
FORCE  TIME GRAPHS FOR IMPACTS 

Definition
Variation of impact forces can be recorded using a force sensor which is connected with long wires to an object. Equal and oppositte forces act on object so variation of force with time is displayed. Average force = change of momentum/contact time 


Term

Definition
When a ball hits a wall it's momentum changes direction due to impact. Velocity and momentum are in the opposite direction if the ball hit the wall straight up; the momentum then has the opposite sign 


Term
REBOUND IMPACTS  CHANGE SPEED 

Definition
If the ball hits the wall with initial speed u, and rebound with speed v in the opposite direction then towards the wall the momentum would be +mu and away is mv this means the impact force will be
Force = (mv)  (+mu) / t 


Term
IF THERE IS NO LOSS OF SPEED ON IMPACT 

Definition


Term

Definition
Initial direction of the ball is not perpendicular to the wall. Components of the velocity must be used. If the angle of which the impact and rebound are the same, no speed is lost. so u=v 


Term
FINAL VELOCITY OF OBLIQUE IMPACTS 

Definition


Term
CHANGE IN MOMENTUM OF OBLIQUE IMPACTS 

Definition


Term
NEWTONS THIRD LAW OF MOTION 

Definition
When two objects interact, they exert equal and opposite forces on each other 


Term
THE PRINCIPLE OF CONSERVATION OF MOMENTUM 

Definition
For a system of interacting objects, the total momentum remains constant, provided no external force acts on the system. 


Term
CHANGE OF MOMENTUM OF TWO COLLIDING OBJECTS 

Definition
They collide then seperate. Momentum of each object changes. Equal and opposite forces exerted on each other when in contact so equal and opposites change in momentum. 


Term
EQUAL AND OPPOSITE CHANGES IN MOMENTUM 

Definition
One object gains momentum and the other object loses momentum 


Term

Definition
total final momentum = total initial momentum 


Term
COLLIDING OBJECTS TICKING TOGETHER 

Definition
They have the same final velocity 


Term
TESTING CONSERVATION OF MOMENTUM 

Definition
Mass of trolleys measured before the test. Trolley A is pushed towards B at a constant velocity. They both stick on impact. Computer records change in velocity.
Measurements should show that
(m_{b}+m_{a})V = m_{a }u_{a} 


Term

Definition
If initial momentum of one object is exactly equal and opposite to that of the other object, the total momentum after the collision will be zero because they cancel out. 


Term
VECTOR NATURE OF MOMENTUM 

Definition
If the final momentum is in the other direction to the first object then it will be . if it's in the same direction it will be + 


Term

Definition
Stop vehicles from entering the opposite carriageway. Strongest barrier are designed to ithstand the impact of a 38 tonne heavy good s vehicle at an angle of 20º and at 40mph 


Term

Definition
Elastic  loses no kinetic energy. e.g a ball will have the same amount of kinetic energy before the impact and after the impact.
NO LOSS OF KINETIC ENERGY 


Term

Definition
Lose kinetic energy. Colliding objects may stick together 


Term
PARTIALLY INELASTIC COLLISION 

Definition
Colliding objects move apart and have less kinetic energy after the collision than before. 


Term
KINETIC ENERGY AFTER/BEFORE A COLLISION 

Definition


Term
KINETIC ENERGY IMMEDIATELY BEFORE IMPACT 

Definition
Loss of potential energy = mgH 


Term
KINETIC ENERGY IMMEDIATELY AFTER IMPACT 

Definition
Gain of potential energy = mgh 


Term

Definition
h/H Gives the fraction of the inital energy that is recovered as kinetic energy after the collision. 


Term

Definition
Always conserved in collisions. Energy is always conserved, but it may be transferred into other forms 


Term

Definition
Two objects fly apart  recoil from each other with equal and opposite amounts of momentum move away in opposite directions. 


Term

Definition
Ratio of speed is the inverse to the mass ratio 

