p2.1 Flashcards
What are the learning outcomes for measuring distance, time, and speed?
- Describe how to measure distance and time in a range of scenarios
- Use measurements of distance and time to calculate speed
- Make calculations using ratios and proportional reasoning to convert units and compute rates
- Apply formulae relating distance, time, and speed for uniform motion
- Calculate average speed for non-uniform motion
Specification reference: P2.1a, P2.1b, P2.1c, P2.1g, P2.1h
How do you plan an investigation to find the average speed of a trolley down a ramp?
Find the time it takes a trolley to travel a set distance down a ramp, and use the formula to calculate average speed. Then change the surface and repeat.
This involves measuring time and distance for different surfaces.
What does ‘non-uniform motion’ mean?
Motion where speed changes over time.
How do you measure distance and time in the laboratory?
- Use a ruler to measure distance
- Use a stopwatch or light gates to measure time
Light gates start and stop a timer when an object interrupts a light beam.
What is the best device to obtain a precise measurement of the length of an aeroplane?
Ultrasound or a motion sensor connected to a computer.
What is the equation linking distance, speed, and time for uniform motion?
distance travelled (m) = speed (m/s) X time (s)
How do you calculate average speed for non-uniform motion?
average speed (m/s) = total distance (m) / total time (s)
What is the SI unit of distance and time?
- Distance: metre (m)
- Time: second (s)
How many metres are in a kilometre?
1000 m
How many seconds are in an hour?
3600 s
Convert 30 mph to m/s.
13 m/s
Steps: 1) Convert miles to metres: 30 miles x 1609 m/mile = 48270 m; 2) Convert hours to seconds: 1 hour x 3600 s/hour = 3600 s; 3) Use speed equation: speed = distance / time.
What is the formula for calculating speed?
speed = distance / time
How do you calculate the distance to the Moon using the speed of light?
Distance = (Speed of light x Time) / 2
Example: If it takes 2.8 seconds for a pulse of light to return.
What are error bars used for in measurements?
To represent uncertainties in measurements on a graph.
True or False: The average speed of a sprinter is the speed maintained throughout the race.
False
Fill in the blank: The motion of a sprinter is __________.
non-uniform
What is the approximate conversion factor when converting between mph and m/s?
About half
What is acceleration?
The change in velocity per second.
What does uniform acceleration mean?
The acceleration does not change.
How do you calculate acceleration?
acceleration (m/s²) = change in velocity (m/s) / time (s)
What is the unit for acceleration?
m/s²
What does an acceleration of 5 m/s² signify?
The speed increases by 5 m/s each second.
What is the change in velocity if a motorcycle accelerates from 0 to 60 mph?
+60 mph = +27 m/s
How do you calculate change in velocity?
change in velocity (m/s) = final velocity (m/s) - initial velocity (m/s)
What is the acceleration of a motorcycle that reaches 60 mph in 2.4 seconds?
+11 m/s²
Fill in the blank: The acceleration due to gravity is ______.
9.81 m/s²
What does negative acceleration indicate?
The object is slowing down.
Calculate the acceleration of a car changing from +20 m/s to -5.0 m/s in 10 seconds.
-2.5 m/s²
True or False: It is better to say ‘negative acceleration’ rather than ‘deceleration’.
True
What is the initial velocity of a lorry with an acceleration of -6 m/s² that ends up at +20 m/s after 4 seconds?
Initial velocity is greater than final velocity.
Explain the significance of using + or - signs with velocities.
They show the direction of motion.
Describe the scenario of a blue car and a red car in terms of speed change.
The blue car is speeding up, the red car is slowing down.
What should you always do when calculating acceleration?
Subtract the initial velocity from the final velocity.
What happens to an object’s downward velocity every second when falling due to gravity?
It increases by about 10 m/s.
What is the formula for calculating acceleration using initial and final velocities?
acceleration (m/s²) = (final velocity - initial velocity) / time
What does a distance-time graph tell you about an object’s journey?
It tells you about the speed of an object on its journey.
What does the slope of a distance-time graph represent?
The speed of the object.
What does a straight line on a distance-time graph indicate?
The object’s speed is constant.
What does a horizontal line on a distance-time graph indicate?
The object is not moving.
What does a steeper line on a distance-time graph indicate?
The object is travelling faster.
How do you calculate speed from a distance-time graph?
Speed = change in distance / change in time.
Fill in the blank: The change in distance in the example was _______ m.
3000
Fill in the blank: The change in time in the example was _______ s.
125
What is the calculated speed from the distance-time graph example?
24 m/s
How is a distance-time graph different from a displacement-time graph?
A distance-time graph shows total distance travelled; a displacement-time graph can have positive, zero, or negative gradients.
What does the gradient of a displacement-time graph represent?
The velocity, which has direction as well as magnitude.
What is the velocity calculated from the displacement-time graph example?
-0.64 m/s
True or False: The gradient of a distance-time graph can be negative.
False
State how you know that the cat is running faster than the dog in the distance-time graph.
The cat’s line is steeper than the dog’s line.
What should you do when axes are shown in units with prefixes?
Convert to standard units.
What is the relationship between distance and time in the context of these graphs?
Distance is plotted against time to show the motion of an object.
What is the significance of a right-angled triangle drawn under the line in a distance-time graph?
It helps to find the change in distance and time for speed calculation.
Describe the journey shown in the distance-time and displacement-time graphs.
The journey involves changes in distance and displacement over time.
Sketch a displacement-time graph for a ball that you throw up in the air.
The graph would show an increase in displacement as the ball rises, followed by a decrease as it falls.
What is an appropriate label for the y-axis in a journey graph?
Distance or Displacement
Calculate the speed in all three sections of the graph.
Speed calculations depend on the distance and time for each section.
