Motion Flashcards
What is the formula for average speed
Distance travelled divided by time taken
What does a horizontal straight line on a distance time graph represent
A stationary object
What does a straight slope on a distance time graph represent
An object moving at a constant speed
What is instantaneous speed
The speed of an object over a very short period of time
How can you find instantaneous speed from a distance time graph
Draw a tangent to the graph at the given time and calculate its gradient
Should the gradient triangle be large or small
As large as possible to reduce percentage uncertainty
What are the features of a scalar quantity
It has only a magnitude with no direction
What are the features of a vector quantity
It has magnitude and direction
Is displacement a vector or scalar quantity
Vector
Is speed a vector or scalar quantity
Scalar
What is the formula for average velocity
Change in displacement divided by time taken
What is the formula for acceleration
Change in velocity divided by change in time
Is acceleration a vector or scalar quantity
Vector because its determined from velocity which is also a vector
How can the acceleration of an object be found from a velocity time graph
By calculating the gradient
What does a curve on a velocity time graph suggest
A changing acceleration
How can displacement be found from a velocity time graph
By calculating the area under the graph
What are the equations of motion known as
The SUVAT equations
What does each letter of SUVAT stand for
Displacement, initial velocity, final velocity, acceleration and time
What is stopping distance
Total distance travelled between the moment a reason to stop is identified and the vehicle becoming stationary
What are the two components of stopping distance
Thinking distance and braking distance
List the main factors that affect stopping distance
Speed, condition of brakes, tyres, roads, weather and alertness
What is the formula for thinking distance
Speed multiplied by the reaction time
What does it mean to be in freefall
When an object is accelerating under gravity with no other forces acting on it
Describe the basic idea for determining G
Drop a heavy ball over a known distance and time its descent, the issue with this is that it all occurs very quickly
Describe the electromagnet and trapdoor method for determining G
An electromagnet holds a steel ball above a trapdoor, when the current switches off a timer is triggered and the magnet releases the steel ball, when hitting the trapdoor the timer is stopped
What causes inaccuracy in the electromagnet and trapdoor method for determining G
Air resistance and the slight delay of timers, this can be improved by using a heavier ball and a much longer drop
Describe the light gate method for determining G
Two light beams are set up one above the other, with detectors connected to a timer. When the ball falls through the first beam the timer is started and when it hits the second the timer is stopped, the distance is known.
Describe the taking pictures method for determining G
A small metal ball is dropped from rest next to a meter rule, the fall is recorded on video or a rapid fire camera is used to capture the event, alternatively a stroboscope illuminates the scene with rapid flashes, the video can be examined to calculate G
How can G be determined from plotting a graph
A distance against time squared graph will have half the value of G
How are vertical and horizontal components of velocity treated
independently of each other
Why does horizontal velocity remain constant
The result would be g cos 90 which results in zero
How is actual velocity found given horizontal and vertical
v = sqrt(horizontal v^2 + vertical v^2)
How is the angle to the horizontal found
Inverse tan of vertical velocity divided by horizontal velocity
Write a statement for horizontal velocity
v cos theta
Write a statement for vertical velocity
v sin theta
