OCR AS Level Physics: Motion
How to calculate vertical displacement and time of flight from projectile motion
Equations of motion
How to calculate speed from a distance-time graph
Gradient
How to find acceleration from a velocity-time graph
Gradient
What does the range of a projectile depend upon?
Height from which it is fired, initial velocity
How does horizontal velocity change in projectile motion?
It doesn't
Why is acceleration a vector?
It is determined by velocity
What do lines with a negative gradient represent on a displacement-time graph?
Object returning to its original position
What does a straight, sloping line with constant gradient on a distance-time graph symbolise?
Object with a constant speed
Why average speed is bad for seeing if someone has gone over the speed limit
People can go over the speed limit for part of the journey and then go way below for other parts and this would even out to show that the average speed is below the speed limit, even though the person has gone above it.
Acceleration
Rate of change of velocity
Distance is what type of quantity?
Scalar
What is the gradient of a distance-time graph?
Speed
Instantaneous speed
Speed of a car over a very short time interval.
Equation for actual velocity of a projectile using a tangent to a point
Square root of Vx^2 + Vy^2 (Think Pythagoras basically. I know I've written it weirdly, sorry!)
What does a straight horizontal line on a distance-time graph symbolise?
Stationary object
How is a stationary object shown on a distance-time graph?
Straight horizontal line
How to show an object with a constant speed on a distance-time graph
Straight, sloping line with constant gradient
How to find instantaneous speed
Tangent to a point
Why does a projectile follow a curved path?
The vertical velocity increases with time but the horizontal component remains the same.
In a projectile, how are vertical and horizontal motions related?
They're not
Equation for thinking distance
Thinking distance = Speed x Reaction Time
Acceleration is what type of quantity?
Vector
Displacement is what type of quantity?
Vector
Velocity is what type of quantity?
Vector
What does the gradient of a displacement-time graph symbolise?
Velocity
Video camera method of determining g
Video camera on rapid fire mode, camera shutter held open, ball dropped, picture produced showing multiple images of the falling ball, plot a distance-time graph, gradient of g/2
Free fall
When the only force acting on an object is its acceleration due to gravity
Derivation of v = u + at
a = v-u/t, at = v-u, -v + at = -u, -v = -u - at, v = u +at
How does vertical velocity change in projectile motion?
g
Symbol for acceleration of free fall
g
Unit of acceleration
ms^-2
Unit of acceleration of free mass
ms^-2
Derivation of s = 1/2(u+v)t
s is a trapezium under a graph where u and v are parallel sides and t is the perpendicular separation between them. The calculations for area of a trapezium give this equation.
Equation for angle of projectile to the horizontal
tan^-1(Vy/Vx)
Equation for horizontal component of velocity at an angle in projectile motion
vcostheta
Equation for vertical component of velocity at an angle in projectile motion
vsintheta
Basic principle of experiments to determine g
Drop a heavy ball over a known distance and time it
Initial vertical velocity when not launched at an angle
0 ms^-1
Speed of an object at highest point
0 ms^-1
Component of g in the horizontal direction
0 ms^-2
What the gradient of a velocity-time graph represents
Acceleration
Equation for acceleration
Acceleration = Change in velocity / Time
What does the value of g depend on?
Altitude, latitude, geology
What the derivation of s = ut + 1/2at^2 is based on
Area under a velocity-time graph
How to find displacement from a velocity-time graph
Area underneath the graph
Equation for average speed
Average speed = Distance travelled / Time taken
Equation for average velocity
Average velocity = Change in displacement / Change in time
Electromagnet and trapdoor method of determining g
Ball attached to electromagnet, current switched off in electromagnet, timer triggered, electromagnet demagnetises, ball falls, hits trapdoor, electrical contact is broken, timer stops
Light gate method of determining g
Ball falls through first beam, timer starts, ball falls through second beam a known distance away, timer stops
Issue with the electromagnet and trapdoor method of determining g
Delays in timing
What the area under a velocity-time graph symbolises
Displacement
Thinking distance
Distance travelled between realising you have to brake and applying the brake
Stopping distance
Distance travelled between seeing a reason to stop and actually stopping
Braking distance
Distance travelled from the time the brake is applied until the vehicle stops