P2.1 Flashcards
Scalar vs vector
Scalar= magnitude (like distance ) speed Vector = magnitude and direction (like displacement) so velocity
Direction represented by + or -
Speed and velocity formulas with SI unit
What is uniform vs non uniform motion
What can you use for accurate distances?
How many metres in a mile?
Speed (m/s) = Distance (m) / time (s), average is total
Velocity (m/s) = Displacement (m) / time(s) but with direction
Displacement is distance from place of start
Where speed changes is called non - uniform motion, but when you stay same speed then uniform. Like running you probably not same speed all the time, so non uniform
ULTRASOUND!! Then measuring tape etc for like falling objects etc
1609
Acceleration formula
Acceleration (m/s2)= change of velocity (m/s) / time (s)
5 m/s2 means every second it increases by 5m speed
Equation of motion for distance velocity and acceleration (uniform)
YOU CAN ONLY USE THIS IF IT IS UNIFORM, as soon as acceleration changes, you have to use something else…
Also, converttttt into m/s (velocity ) first
V2- u2= 2AD
Final velocity 2 - initial velocity 2 = 2 X acceleration X distance
Kinetic energy
0.5 M V 2 (j)
PRACTICAL : Investigating speed and acceleration
Set up a ramp, and 3 light gates, which tell you the exact time an object passed through it , which is better then using a stopwatch for reaction time (human error). Measure distances between 3 spots. Then drop a trolley from the ramp.
Speed can be calculated when it comes off the ramp, or average speed when it is accelerating down the ramp.
Acceleration can be found by doing final velocity (which is the speed on the smooth part) - initial which is 0 / time between the light gates in the first two points on the ramp.
1) if you increase height of ramp, distance ramp holds, or decrease friction you can increase the final speed on the runaway and acceleration on ramp.
In general use instruments bigger then what you are measuring. More then 5 seconds you can do stopwatch other then that light gate.
Distance time graphs key points
Find speed when it’s curved?
1) tell you how far so entring has Travelled against time
2) therefore the gradient of the distance time graph is the SPEED. IF IT IS CURVED, draw a tangent
3) - flat sections show object has stopped moving
- steeper section shows increase of speed (steeper gradient more speed)
- flat but diagonal line means steady speed
- steeping curve means increase of ACCELERATION
TANGENT
- levelling off curve shows DECELERATION, decreasing its speed.
Velocity time graph key points
1) Gradient = acceleration
- flat section = steady velocity
- straight but diagonal line means CONSTANT acceleration/ deceleration
- curve means increasing or decreasing acceleration
- area under graph represents the distance travelled in that time.
- velocity at any time is just reading off the axis.
To calculate distance, find out how far one square represents, then count squares or use area to find out how many squares and multiply these.
Also displacement time graph
- gradient gives velocity, therefore the gradient can be positive, zero or negative, as it shows a direction too…
How you can make your graphs…
1) if you have distance travelled and time= you can make a distance time graph, gradient is speed, so you can make speed time graph, and gradient is acceleration (just magnitude)
2) if you have distance travelled from a start point you can make a displacement time graph where the gradient is velocity, then you can make a velocity time graph where gradient is acceleration.
How do you add vectors from perspective pints?
If you are in opposite directions then perspectives you add them
If it’s the same direction then minus them
