Module 3 - Forces and Motion Flashcards
Acceleration
The rate of change of velocity
Average speed
Distance over time for the entire region of interest
Braking distance
The distance travelled between the breaks being applied and the vehicle coming to a stop. It is affected by the vehicle and road conditions.
Displacement
The direct distance between an object’s starting and ending positions
It is a vector quantity and so has both a direction and magnitude
Displacement - Time graphs
Plots showing how displacement changes over a period of time
The gradient gives the velocity
Curved lines represent an acceleration
Free-Fall
An object is said to be in free fall when the only force acting on it is the force of gravity
Instantaneous speed
The exact speed of an object at a specific given point
Projectile motion
The motion of an object that is fired from a point and then upon which only gravity acts.
(when solving projectile motion problems, it is useful to split the motion Into horizontal and vertical components)
Reaction time
The time taken to process a stimulus and trigger a response to it. It is affected by alcohol, drugs and tiredness.
Stopping distance
The sum of thinking distance and breaking distance for a driven vehicle
Thinking distance
The distance travelled in the time it takes for the driver to react. It is affected by alcohol, drugs and tiredness.
Velocity - Time graphs
Plots showing how velocity changes over a period of time.
The gradient gives acceleration.
Curved lines represent changing acceleration.
Velocity
The rate of change of displacement.
It is a vector quantity and so has both a direction and magnitude.
What does a straight, horizontal line represent on a displacement-time graph?
A stationary object
What does a line with a constant, non-zero gradient represent on a displacement-time graph?
An object moving with constant velocity.
What does a curved line represent on a displacement-time graph?
Acceleration (if gradient is increasing)
Deceleration (if gradient is decreasing)
What does a straight, horizontal line represent on a velocity-time graph?
An object moving with constant velocity.
What does a line with a constant, non-zero gradient represent on a velocity-time graph?
An object that is accelerating (positive gradient)
An object that is decelerating (negative gradient)
What does the area under a velocity-time graph represent?
Displacement
What does the area under an acceleration-time graph represent?
Velocity
Describe how the terminal velocity of an object can be determined using light gates.
Set up the light gates vertically and measure the distance between them.
Connect them to a data logger and then release an object from rest above them, measuring the time it takes for the object to travel between the two gates.
Using the time and the known distance, you can calculate the velocity of the falling object.
Describe how light gates can also be used to investigate conservation of momentum.
Place two carts on a linear air track (to reduce friction) with repelling magnets so that they do not stick together.
Attach card to the top of each cart so that they break the beams of the light gates when they pass.
Keep one cart stationary and push the other towards it, measuring its velocity before the collision.
Then measure the velocity of both carts after the collision and calculate the momentum before and after.
Define ‘g’.
It is the acceleration of an object in response to the gravitational attraction between the earth and the object.
Describe the experiment in which one can determine ‘g’ using an electromagnet.
An electromagnet holds a steel ball suspended a measured distance above a surface, then start the timer when the electromagnet is deactivated, and stop it when the surface is hit.
As the ball was initially resting, u = 0
The distance and time are known, so we can use the SUVAT equation: s = ut + 1/2at^2t
Calculate ‘a’ which, in this, is ‘g’.
