Scalar
A quantity with magnitude ( size ) only
Examples : mass, time energy, distance, speed
Vector
A quantity with magnitude and direction
Examples : displacement, force, momentum, acceleration, velocity
Distance
How far apart 2 points are
Scalar quantity
Displacement
A distance in a certain direction
Vector quantity
Velocity
Speed in a given direction
Vector quantity
Speed
How fast an object moves
Scalar quantity
Acceleration
the rate of change of velocity
Vector quantity
Reaction time
Time it takes to respond to a stimulus
Stopping distance
the sum of the distance the vehicle travels during the driver’s reaction & the braking distance
Thinking distance
How far the car travels in the reaction time
Braking distance
How far the car travels with the brakes applied until stopping
Adding scalars
Add individual values
Adding vectors in the same direction
Add the individual magnitudes of the vectors ( direction doesn’t change )
Adding vectors in the opposite directions
Subtract magnitude of vectors
Direction is towards the large vector
Adding vectors in different directions
Use scale diagrams and ‘ tip to tail ‘ method
Tip to tail method
- Choose a suitable scale ( smaller distance = more errors )
- Draw one vector to scale
- Draw the second vector
with its tail at the tip of the 1st vector
in the correct direction - Connect the tail of the 1st vector with the tip of the final vector
Measure the arrow and it’s direction
Label the angle on diagram
Distance time graph features
Steep line - fast
Straight horizontal line - stationary
Shallow line - slow
Straight diagonal lines - constant speed
Gradient = speed
Velocity time graph features
Tells us how velocity varies over time
Features :
Gradient = acceleration
Area under graph = distance travelled
Area of a regular shape - use geometry calculations
Irregular shapes - count the squares
Factors that affect the reaction time / thinking distance
BE SPECIFIC TO Q
1. Alcohol / drugs
2. Tiredness / illness
3. Distractions
Factors that affect the braking distance
BE SPECIFIC TO Q
1. Brakes quality
2. Surface conditions ( wet/icy/type )
3. Tyre condition
4. Weight
A factor that affects the thinking distance and braking distance
Speed
What is speed directly proportional to?
Thinking distance
What is the braking distance proportional to?
Speed squared
Walking
1.5m/s
