SP1a-d Motion Flashcards
Weight
A force that acts towards the centre of the Earth. All forces have both magnitude and direction. Measured in Newtons.
Vector quantities
Quantities that have both size and direction.
e.g. forces
How are forces shown
They are shown on diagrams using arrows, with longer arrows representing larger forces.
Mass
Mass measures the amount of matter in something and does not have a direction.
Scalar quantities
Quantities that do not have a direction.
e.g. distance, speed, energy, time
Displacement
The distance covered in a straight line, and has a direction. Displacement at the end of a journey is usually less than the distance traveled because of the turns or bends in the journey.
Velocity
Speed in a certain direction.
e.g. a car may have a velocity of 20 m/s northwards.
Acceleration
A measure of how fast velocity is changing. (vector)
Momentum
A combination of mass and velocity. (vector)
Units for speed
meters per second (m/s)
kilometers per hour (km/h)
miles per hour (mph)
Instantaneous speed
The speed at a particular point in the journey
Speed calculation
(average)speed (m/s) =
distance (m) / time taken (s)
Distance equation
distance travelled (m) =
average speed (m/s) x time (s)
Speeds of common things
Walking = 1.4 m/s
Cycling = 6 m/s
What do distance/time graphs tell you about speed
- Horizontal lines mean the object is stationary
- Straight, sloping lines mean the object is travelling at a constant speed.
- The steeper the line, the faster the object is travelling
- The speed is calculated from the gradient of the line.
Acceleration calculation
acceleration (m/s)² =
change in velocity (m/s) /
time taken (s)
a= (v-u)/t
What does acceleration show
A change in speed or direction
What can acceleration be related to + equation
Initial velocity
Final velocity
distance travelled
v² - u² = 2 x a x (x)
Acceleration due to gravity
9.8 m/s². Represented by the symbol g. It is often rounded to 10 m/s² in calculations.
Deceleration
Acceleration with a negative value.
What does an acceleration of 10 m/s² mean.
That each second the velocity increases by 10 m/s
What does a negative velocity (a line below the horizontal axis) mean on a Velocity/time graph
It shows the object is moving in the opposite direction.
How do you calculate distance travelled from a velocity/time graph
The area under the graph is the distance the object has travelled.
(distance is calculated by multiplying a velocity and a time.)
What is a light gate
A switch that reacts when something passes between the optical transmitter and receiver, breaking the light beam.
