Calculating from displacement-time graphs: including tangents (v=s/t)
I can take readings from displacement-time graphs to find distance, displacement, speed and velocity.
Calculating from displacement-time graphs: including tangents (v=s/t)
I can take readings from displacement-time graphs to find distance, displacement, speed and velocity.
Slide deck
Lesson details
Key learning points
- Velocity of an object is equal to the gradient of a displacement-time graph.
- A direction in which velocity and displacement are measured needs to be chosen.
- A negative gradient on a displacement-time graph (sloping downwards) represents velocity in the opposite direction.
- A negative value for displacement represents a position ‘behind’ the starting position.
- Instantaneous velocity of an object is equal to the gradient of a tangent to a displacement-time curve.
Common misconception
A pair of coordinates on a d-t graph can be used to calculate the instantaneous speed or velocity at that point, but that only works for a straight line graph through the origin.
Ask pupils to calculate the velocity of a graph that represents a steady velocity on a line that does not go through the origin, and to check to see if dividing the values at any point on the line gives the right value for velocity.
Keywords
Displacement-time graph - A displacement-time graph shows the change in displacement over a time period. The displacement along a straight line can be positive or negative.
Gradient - The gradient on a displacement-time graph gives the instantaneous velocity.
Tangent - A tangent drawn to the gradient on a curving displacement-time graph will give the instantaneous velocity.
Instantaneous velocity - The instantaneous velocity is the velocity of an object at a particular moment in time.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Video
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Worksheet
Starter quiz
6 Questions
a vector measured in m
a vector measured in m/s
a scalar measured in m
a scalar measured in m/s
Exit quiz
6 Questions
a graph showing distance in a given direction over a period of time
the steepness of a line or slope
how fast an object moves in a given direction
how fast an object moves in a given direction over a period of time
