Motion
Remember that gravity = 9.81 m/s^2 (it is acceleration)
Scalars and Vectors
Scalar - Something with only magnitude e.g. Speed, mass, temperature
Vector - Something with magnitude and direction e.g. velocity, current, acceleration
Vector - Something with magnitude and direction e.g. velocity, current, acceleration
vector + vector = vector
scalar + scalar = scalar
vector x scalar = vector
scalar x scalar = vector
vector x vector = scalar
scalar + scalar = scalar
vector x scalar = vector
scalar x scalar = vector
vector x vector = scalar
Resolving Vectors
When there are two vectors the overall vector can be calculated by a vector triangle. This is done by actually drawing to scale the vectors involved. This enables you to work them out. To solve one of the vectors you need two of the other vectors in th vector triangle.
Kinematics
Acceleration - Rate of change of velocity
Velocity - Rate of change of displacement
Displacement - Distance in a certain direction
Average Speed - The average speed over a period of time
Instantaneous Speed - The speed at a certain point in time
Velocity - Rate of change of displacement
Displacement - Distance in a certain direction
Average Speed - The average speed over a period of time
Instantaneous Speed - The speed at a certain point in time
Displacement-time Graph
A positive gradient shows the object is moving forward
0 gradient shows the object is still
A negative gradient shows the object is returning back
The gradient gives the velocity
Velocity-time Graph
A negative gradient shows the deceleration
The gradient gives the acceleration
Linear Motion
'suvat' equations - equations of constant acceleration in a straight line
s = displacement (m)
u = initial velocity (m/s)
v = final velocity (m/s)
a = acceleration (m/s^2)
t = time (s)
s = displacement (m)
u = initial velocity (m/s)
v = final velocity (m/s)
a = acceleration (m/s^2)
t = time (s)
Galileo and Aristotle
Aristotle believed that the rate of fall was proportional to an objects mass. This meant that they accelerated at different rates. Galileo proposed that an object will fall at the same rate as an object of different mass. This can be shown in a vacuum. What actually affects the rate of fall is the surface area. Galileo proved this by dropping two cannon balls of different masses off the leaning tower of pisa. Although they didn't land at the same time he disproved Aristotle because using Aristotle's theory the two objects should have hit the floor much further apart in time |
Gravity
As gravity is acceleration caused by an objects gravitational energy.
An experiment to find it can be set up to discover what the magnitude of gravity is. A trap door and electromagnet method can be used.
An experiment to find it can be set up to discover what the magnitude of gravity is. A trap door and electromagnet method can be used.
The acceleration over 's' can be discovered with the equation g = 2s/t^2
This does have problems and in the exam they might ask you why.
This does have problems and in the exam they might ask you why.
- If the electromagnet's current is too large there will be a delay in letting the ball fall from the electromagnet after the current is switched off
- If the distance is too large air resistance might have an affect on acceleration
- If the distance isn't accurately measured this will drastically affect the result
- The accuracy of the timer also means that it's harder to get an accurate result