Speed>>> =distance / time
Velocity>>> Is a vector and therefore has both direction and magnitude.
=displacement / time
Accelaration>>> =(v-u)/t
Where
... [Show More] v is initial velocity and u is final velocity
Displacement time graph>>> upward slope - constant positive velocity
flat line - stationary
downward slope - negative constant velocity
It can often be easier to just draw a distance-time graph.
velocity-time graph>>>
Acceleration-time graph>>> a graph describing motion of an object, with acceleration on the vertical axis and time on the horizontal axis.
upward slope - increasing acceleration
flat line - constant acceleration
downward slope - decreasing acceleration
Adding vectors>>> Draw both vectors next to each other head to tail and then use Pythagoras and/or trig to calculate the missing side of the triangle and the angle.
Remember, in order to draw these correctly, you'll probably have to move one of the vectors.
Moments>>> the turning, movement of a force.
=force x perpendicular distance from the pivot.
Principle of moments>>> For an object that is in equilibrium:
- the sum of the clockwise moments = the sum of the anticlockwise moments
- There is no resultant force.
Centre of gravity>>> The point where the entire weight of an object appears to act.
This is essentially the same thing as the centre of mass
This always lies along the line of symmetry. for a flat irregular object hang it from different points and draw a line straight down. Where the lines connect that's the centre of mass, because it will always hang directly under a point of suspension.
For other irregular objects it can be found using moments.
Newton's First Law>>> An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Newton's Second Law>>> F=ma
Newton's Third Law>>> For every action there is an equal and opposite reaction
Kinematics>>> s = displacement
u = initial velocity
v = final velocity
a = acceleration
t = time.
All of the equations apart from s = (u+v)/2 xt are given in the formula book. Just use them.
Resolving vectors>>> A single diagonal vector can also be broken down into it's horizontal and vertical components. The principle is the same as when finding resultant vectors.
projectile motion>>> When objects are thrown up into the air or kicked off a cliff or something similar, they move in a curved line.
By separating the horizontal and vertical components of this motion we can calculate distances, times and velocities etc.
The vertical component just goes straight up and down and has acceleration due to gravity.
gravitational potential energy>>> The energy that an object has by virtue of it's position in a gravitational field.
= mgh
Kinetic energy>>> the energy an object has by virtue of its movement
= ½mv²
Transfer of energy>>> When an object falls, gravitational potential energy is converted into kinetic energy. This happens as energy must be conserved.
For this specific conversion, you don't even need to know the mass of the object as mgh=½mv² and therefore the Ms cancel out, leaving you with gh=½v²
In this conversion you assume that air resistance can be ignored
Work done>>> force × distance moved in the direction of the force
It is measured in Joules. This is the same as energy transferred
Work done at angles>>> In order to find out work done, you need to resolve the forces to find the component of a force that is acting in the direction of motion.
Power>>> = energy transferred/time taken
Measured in Watts
Efficiency>>> =useful energy out/total energy in
=useful power output/total power input
Momentum>>> p=mv (momentum is the product of mass and velocity)
Momentum & Newton's 2nd Law>>> *The rate of change of momentum of a body is directly proportional to the resultant force applied to the body, and is in the same direction as the force*
This is because:
F=ma and a=(v-u)/t
F=m(v-u)/t
F=dp/dt -> this is the rate of change of momentum.
This is the mathematical way of writing a rate of change but we can write the average change of small timescales as Δp/Δt
Conservation of linear momentum>>> In a closed system the sum of total momentum before a collision/explosion is the same as the sum of total momentum after the collision/explosion.
Momentum and newtons third law>>> Momentum is responsible for Newtons third law. As momentum in a closed system (in this case a very big system such as our whole earth etc.) must be conserved, if a [Show Less]