2.1: Distance, Speed and Acceleration Flashcards
What is a force and what does it do?
A force is a push or a pull, and it changes the position, shape and motion of an object.
What is the equation for speed?
Speed = Distance/Time
What shows the difference between speed and velocity?
The direction of movement is clarified with velocity - speed is a scalar quantity, meaning it has magnitude but no sense of direction
What is the equation for velocity?
Velocity = Displacement/Time
Define a Scalar.
Measurements that have a magnitude (size).
Define a Vector.
Measurements that have size and direction. Velocity is a vector quantity.
What is the equation for acceleration?
Acceleration = Change in Velocity/Time
What is a speed-time graph?
A speed-time graph shows the motion of an object through a certain period of time. A straight line upwards or downwards represents a constant speed, a curve showing gradual acceleration and a flat horizontal line showing it stationary.
What is a velocity-time graph?
A velocity-time graph shows the motion of an object in one direction through a certain period of time. A straight line upwards or downwards represents a constant speed, a curve showing gradual acceleration and a flat horizontal line showing it stationary.
What does the area under a velocity-time graph represent?
The distance travelled
How do we calculate stopping distance?
Thinking distance + braking distance
When has a vehicle stopped?
When its speed is 0m/s
What increases more significantly in stopping times when extra speed is added?
Braking distance, although thinking distance goes up too
Name four factors that affect stopping distances
The velocity of the car
The reaction time of the driver
Whether the driver is distracted
The condition of the tyres
What is the equation for resultant force?
F (N) = change in momentum (kg m/s) / time for change (s)
What are the two ways of reducing the force on the occupants?
By reducing the speed of the collision and so reducing the change of momentum
By increasing the time for the collision
What is speed?
A measure of how fast an object is moving
Why is speed a scalar quantity?
Because it only has magnitude
Why is velocity a vector?
Because it has direction as well as magnitude
What is velocity measured in?
Metres per second, and in a specific direction
What is accelaration?
The rate of change of velocity
What is the equation for accelaration?
Acceleration = change in velocity/ time
What are the units of accelaration?
Metres per second squared
How can the speed of an object be found?
By measuring the gradient of the graph
How do you work out the gradient?
The difference in height (y coordinates), divided by the difference in width (x coordinates)
What is the area under a velocity time graph?
The distance travelled
What does the safe stopping distance of a vehicle depend on?
The driver’s reaction time and the braking distance of the vehicle
What do traffic control measures include?
Speed limits and speed bumps
What value does speed but not velocity always have
A positive one
