3.1 motion Flashcards
Define speed
the rate of change of distance
What is the equation used to calculate speed
speed = distance/time
(ms^-1)
define displacement
the distance an object has travelled in a given direction, so it is a vector with both magnidue and direction
Define velocity
the rate of change of displacement, or speed, in a given direction (vector quantity)
What is the velocity equation
change of displacement/time (ms^-1)
define acceleration
the rate of change of velocity (vector)
equation for acceleration
change in velocity / time (ms^-2)
What does a straight, horizontal line represent on a displacement-time graph?
A stationary object
What does a line with 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 inc) or deceleration (if gradient dec)
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 (pos gradient) or decelerating (neg 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 obect to travel between the two gates
- Using the time and known distance, you can calc 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’
The acceleration of free fall, ‘g’, is the acceleration of an object in response to the gravitational attraction between the earth and the object. g = 9.81 ms^-2
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 reesting, u = 0
- The distance and time are known, so we can use a suvat equation (s=ut+1/2 at^2)
- calculate ‘a’ which, in this case, is ‘g’
A ball is projected off of a castle at 6ms^-1. How does its horizontal velocity change from its launch until it hits the ground?
The horizontal velocity remains the same as there is no acceleration in the horizontal direction
In projectile motion, what is vertical acceleration?
The vertical acceleration is equal to gravitational field strength (g) downwards
Centre of mass definition
Point of average mass of an object
Centre of gravity definition
The point through which the weight of the object acts
Which two things are required for stability?
Low centre of mass and wide base
Equilibrium definition (Elaine’s)
The sum of the clockwise moments about a point is equal to the sum of anticlockwise moments about the same point
