CP1 Flashcards
What is a vector quantity?
A quantity that have both magnitude and direction.
What is a scalar quantity?
A quantity that has magnitude but no direction.
What is magnitude?
The size of something, such as the size of a force or the measurement of a distance.
What direction does the force of weight act towards?
It acts towards the centre of the earth.
What is displacement and is it a scalar or a vector?
The distance covered in a straight in line a particular direction (e.g. 300m north) and it is a vector.
What are some examples of scalar quantities?
- Mass
- Speed
- Distance
- Energy
What are some examples of vector quantities?
- Force
- Weight
- Acceleration
- Displacement
What is velocity and is it a scalar or a vector?
Velocity is the speed of an object in a particular direction (e.g. 20m/s northwards) and it is a vector.
What is the difference between distance and displacement?
Distance is the measure of how far an object travels whereas Displacement is how far an object has travelled in a particular direction.
What is the difference between speed and velocity?
Speed is the measure of the distance an object travels in a given time whereas Velocity is the speed of an object in a particular direction.
What is acceleration?
A measure of how fast the velocity of an object is changing.
What is momentum?
A combination of mass and velocity.
What is the formula triangle for Speed, Distance and Time?
Distance
Speed | Time
What is the formula to find the average speed?
Average Speed (m/s) = Distance(m)/Time(s)
What are some common units for speed?
m/s, km/h, mph
What is instantaneous speed?
The speed at a particular point in a journey.
What is the difference between instantaneous speed and average speed?
Average speed is the speed across the whole journey while instantaneous speed is the speed at a particular point in a journey.
How do you measure the speed of high-speed objects?
By using lightgates.
What are light gates?
A piece of apparatus containing an infrared beam that is transmitted from a source onto a detector, which can accurately read the speeds of high-speed objects.
Why are light gates used to measure speed of high-speed objects instead of a stopwatch?
As they do not need the error of human reaction time to press the button on the stop watch due to infrared signals immediately being emitted once the object crosses the light gate.
What are some typical speeds in m/s for: Airliners, Cyclists and Walking Humans?
Airliners: 250 m/s
Cyclists: 6 m/s
Walking Humans: 1.4 m/s
What is the speed of sound in m/s?
343 m/s.
What does a horizontal line mean in a distance/time graph?
It means that the object is stationary (its distance from the starting point has not changed).
What does a straight, sloping line mean in a distance/time graph?
It means that the object is travelling at a constant speed.
What does it mean when the line gets steeper in a distance/time graph?
It means that the speed of object is increasing.
How is speed calculated from a distance/time graph?
It is calculated by finding out the gradient of the line.
How do you calculated the gradient of a line
Vertical difference between two points in a graph/Horizontal difference between the same two points (rise/run)
What is the equation for acceleration?
Acceleration(m/sˆ2)=change in velocity(m/s)/time taken (s) (a=v-u/t)
What is the formula triangle for acceleration
V-U
A | T
What do ‘V’ and ‘U’ stand for in the acceleration?
V=Final velocity
U=Initial velocity
What is deceleration?
When an object is slowing down. It is a negative acceleration.
What is the formula for deceleration?
final velocityˆ2 - initial velocityˆ2 = 2 x acceleration x distance ((vˆ2)- (uˆ2) = 2 x a x d)
What is the rate of acceleration due to freefall (when only the force of gravity is acting on an object)?
9.8m/s which is often rounded to 10m/s in calculations.
What does a horizontal line mean in a velocity/time graph?
The object is travelling at a constant velocity.
What does a sloping line mean in a velocity/time graph?
The object is accelerating.
What does a sloping line with an increasing gradient mean in a velocity/time graph?
The steeper the line, the greater the acceleration.
What does a line sloping downwards mean in a velocity/time graph?
The object is decelerating (slowing down).
What does a negative velocity mean in a velocity/time graph?
The object is moving in the opposite direction to the original velocity (e.g. if an object was moving forward in a positive velocity, it would move backwards in a negative velocity)
How do you find the acceleration in a velocity/time graph?
You work out the gradient of a line (rise/run)
How do you find the distance in a velocity/time graph?
By finding the area of a shape in the velocity/time graph.
How do you find the total distance in a velocity/time graph?
By finding the area of all shapes in the velocity/time graph and adding them all together.
Why does the area under part of a velocity/time graph give you the distance covered?
As displacement is velocity x change in time.
