P2.1 - Motion Flashcards
Disadvantage of using a ruler to measure distance
It is difficult to measure very small or very large distances
Disadvantage of using a stopwatch to measure time
There is a reaction time involved with starting/stopping the timer which affects the accuracy and precision
What can be used to measure very short periods of time?
Light gate which automatically stops a timer when an object interrupts a light beam
What can be used to measure distance?
Ultrasound - measures the time taken for a pulse to travel there and back. It calculates distance using this time and speed of the pulse.
Uniform motion
Speed does not change
Non-uniform motion
Where speed does change
Equation s = d/t gives you the average time, how/why?
Because usually your speed is non-uniform. You cannot be moving at 10 m/s constantly hence it is average
SI Unit for distance
Metres, m
SI Unit for time
seconds, s
SI Unit for speed/velocity
metres per ssecond, m/s
How to convert from 1cm3 to m3
(1x1x1) = (100x100x100)
How many metres in a mile?
1609 metres
How many seconds in an hour?
3600 seconds (60x60)
Vector
Gives magnitude and direction - these are represented by arrows, with a given size
Scalar
Shows only magnitude
Distance
Length of the path that is actually taken (this is a scalar)
Displacement
The shortest distance between two points (this is a vector)
Why are vectors more useful?
They provide more accurate information about what a body is doing
What is the difference between speed and velocity?
Speed is a scalar quantity (it only gives magnitude), whereas velocity is a vector quantity (it gives both magnitude and direction)
How to add vector quantities?
- if they go opposite directions, CANCEL OUT
- if they go same direction, ADD
Acceleration
Rate of change of velocity
SI unit for acceleration
m/s^2
Is acceleration a vector?
Yes. - negative acceleration is known as deceleration
Equation for acceleration
a = v-u/t (final v -initial v over time)
