Topic 2: Motion And Forces Flashcards
What do Vector quantities have
Magnitude and direction
Generally vectors can be negative as a certain direction is positive (generally scalars cant be negative)
What do Scalar quantities have
Only magnitude
Generally scalars cannot be negative
(Generally vectors can be negative as a certain direction is positive)
Examples of scalar
Speed
Mass
Distance
Time
Energy
Examples of vector
Velocity
Force
Displacement
Acceleration
Momentum
What to find on a Displacement time graphs
Gradient is velocity
Sharper gradient= faster speed
Negative gradient= slower speed
Horizontal line= stationary
0 distance= back to starting point
Area under line = nothing
Curved line= velocity is changing (acceleration)
What to find on a Velocity time graph
Gradient= acceleration
Sharper gradient= greater acceleration
Negative gradient= deceleration
Horizontal line= constant speed
0 velocity = stationary
Are ynder line= distance travelled
Curved line= acceleration is changing
Methods to determine constant speed
Measure distance travelled
Use stopwatch for time taken
Use speed= distance/ time
Methods to determine average speed
Work out total distance travelled
Find the time taken for the whole journey
Yse speed= distance/ time
Methods to determine light gates
Set up two, one at start and one at end
Measyre distance between them
As soon as the object passes through the first, it will measure the time taken to reach the second
Use speed= distance/ time
(This removes reaction time and human error with a stopwatch - makes it more accurate)
Newtons First Law
An object has a constant velocity unless acted on by a resultant force
If resultant force acts on object it will accelerate
Acceleration= change in vel. over time
Velocity will change
Direction or speed will change (or both)
If resultant force is 0
No acceleration
Moving at constant velocity (same speed and direction)
Or object is stationary
Newtons Second Law
Force = mass x acceleration (F=ma)
where force is in Newtons (N), mass is in kg and acceleration in ms^-2
What is used to measure weight and what is it used for
Weight is measured using a force meter, or weighing scales, and is used to work out mass of unknown object
The greater the gravitational field strength, the greater the weight
Circular motion
Object moving in a circle with constant speed
Speed is constant, direction changes
Velocity chnages (due to direction change)
So it is accelerating
Force
For motion in a circle, there must be a force wich supplies this acceleration
This is called centripetal force, and is directed towards the centre of the curcle
Intertial mass
Measure of how difficult it is to change velocity of an object (including from rest)
Measured by:
internal mass= force/ acceleration
Newtons Third Law
Every action force has an equal and opposite reaction force
