9-Momentum Flashcards
What does the conservation of momentum law state?
That, in any interaction, momentum is conserved.
What does the total momentum before equal?
The total momentum after
What does the total y momentum before equal?
The total y momentum after
What does the total x momentum before equal?
The total x momentum after
Why does a cannon recoil?
Because there is no momentum before firing, but the cannon ball has momentum, which means that the cannon recoils with equal and opposite momentum
What is the unit of momentum?
p
What is momentum measured in?
kgms-1
What is the equation of momentum?
Mass x Velocity
Is momentum a vector or a scalar value?
It is a vector
What is the mass of an object?
The amount of matter in an object
What is the weight of a mass?
The pull of gravity acting on the mass
What is Newton’s first law?
Inertia
What does inertia state?
That the momentum of a body will not change unless a force acts on it
What does Newton’s second law state?
A stronger force will make the momentum change quicker than a weaker force
What equation can you derive from Newton’s second law?
Force = Change in momentum / Time
How do you derive ‘F=ma’?
F = Change in momentum / time = mv/t = m x v/t = ma
What does force x time equal?
The change in momentum
What does Ft get called?
The impulse
What are crumple zones in cars designed to do?
Increase the time taken in a collision
What is the definition of an impulse?
A force acting briefly on an object causing a change in momentum.
What is the equation of acceleration?
Change in velocity / Change in time
What is the area under a force time graph?
The total impulse
What is Newton’s third law?
Momentum is always conserved, so the momentum lost by B is gained by A
If A pulls B in one direction, what does B do?
Pulls A with an identical force in the opposite direction
What does g equal>
9.8ms-2
What is the equation of weight?
Mass x g
What is the weight mg caused by?
The gravitational pull of the earth
If the book is stationary on a table, what does the downwards pull of the earth on the book equal?
The upwards push from the shelf
What happens when you multiply the force by the displacement?
You get the work done by the object
What is work done measured in?
Joules
What does work done equal?
Force x distance
What is energy?
The capacity to do work
If a car decelerates to a halt, what do the brakes do?
They exert a force on the car and do work on the brake linings, heating them.
What is the energy of any moving object called?
The kinetic energy
Why is the kinetic energy less in reality?
There are numerous other forces present, all doing work
What is the equation of kinetic energy?
1/2 mv^2
In the absense of any other forces than gravity, what does F=ma equal?
F=mg
What is the symbol equation of work done (Force x displacement)?
mgh
What is the equation of gravitational potential energy?
Mass x g x height
What is gravitational potential energy?
The work done in lifting that can be transferred from this store if it is allowed to fall
What does the kinetic energy gained equal?
The change in gravitational potential energy
What does the final kinetic energy equal?
The initial kinetic energy + change in gravitational potential energy
What is an object projected outwards called?
A projectile
As the weight (mg) of a body can be resolved into perpendicular components at an angle theta, what equation can you derive?
mg cos(theta)
As weight is a vertical force, what can’t it change?
The horizontal velocity component of a moving object
What affects the weight component of a projectile?
Air resistance
What is the vertical component accelerated downwards by?
Gravity
What happens to the horizontal component of a projectile in motion?
It remains constant, as it is not affected by air resistance
