Motion Flashcards
What is Newton’s first law of motion?
An object will continue in its present state of rest or motion unless acted on upon by an external resultant force
So any object moving at a steady speed in a straight line has..
Zero resultant force acting on it
What is inertia?
The inbuilt tendency for matter to resist any change in its motion
What is Newton’s second law of motion?
If a resultant force (RF) act on an object of a mass (m), it causes an acceleration (a) in the direction of the resultant force
What is the Newton’s Second Law equation for resultant force?
RF = ma
Newtons Kg m/s^2
What is newtons third law of motion?
If object A exerts a force on object B, then object B exerts an equal and opposite force on A
Any moving object has
Momentum
What is the momentum equation?
Momentum = mass x velocity
What is momentum measured in?
Newton seconds (Ns)
or kilogram metres per second (kgm/s)
Momentum is a …… quantity.
Vector quantity
How can Newton’s second law be written in terms of momentum?
RF = change in momentum/time taken
And can be written as:
RF = (mv - mu)/t
If we ignore air resistance, the only force on an object in the air is
It’s own weight
In the absence of other forces, all objects near the surface of the earth fall with the same …
acceleration- the acceleration due to gravity (g) also called the acceleration of free fall
What is the size of the acceleration due to gravity on earth?
10m/s^2
For any isolated system
The total linear momentum is constant
What is an isolated system?
One upon which no external forces act
What is the conservation of momentum?
Total moment before collision = total momentum after collision
What is the equation for the conservation of momentum?
M1U1 +M2U2 = M1V1 + M2V2
What is an elastic collision?
Where total kinetic energy is conserved
What is inelastic collision?
Total kinetic energy before the the collision is greater than the total kinetic energy after the collision. Energy is lost as sound, heat etc
What is a perfectly inelastic collision?
Kinetic energy is lost and the masses stick together after the collision
What is the equation for a perfectly inelastic collision (stick together)?
m1u1 + m2u2 = (m1 + m2)v
What is the definition of work?
Work (w) = Force applied (f) x distance moved (s) in direction of force
What is the equation of work?
W=FS
How much work is done if no motion occurs
No work is done
What is energy?
The ability to do work
What is energy measured in?
Joules
What is the equation for kinetic energy?
K.E = 1/2 mv2
What is the equation for gravitational potential energy?
P.E = mgh
What is the principle of the conservation of energy?
Energy can never be created nor destroyed, it can only be changed from one form to another
What is the link between work and energy?
Work done on or by an object
Energy gained or lost by an object
What is power?
Rate of doing work
What is the equation for power?
Power = Work done / Time taken
P=W/t
What is efficiency?
A way of describing how good a device is at transferring energy from one form to another in an intended way
What is the equation for efficiency?
Efficiency = Useful energy out / Total energy in
