1.1.1 - 1.1.7 - Movement ad position

Question 1

What is a distance time graph?

Answer 1

A distance-time graph shows how the distance of an object moving in a straight line (from a starting position) varies over time:

Question 2

What information do distance time graphs show?

Answer 2

If the object is moving at a constant speed
How large or small the speed is

Question 3

What is different speed represented by on a distance time graph?

Answer 3

A straight line represents constant speed
The slope of the straight line represents the magnitude of the speed:
A very steep slope means the object is moving at a large speed
A shallow slope means the object is moving at a small speed
A flat, horizontal line means the object is stationary (not moving)

Question 4

How is moving at a changing speed represented?

Answer 4

Objects might be moving at a changing speed
This is represented by a curve
In this case, the slope of the line will be changing
If the slope is increasing, the speed is increasing (accelerating)
If the slope is decreasing, the speed is decreasing (decelerating)

Question 5

What does a gradient of a distance time graph show?

Answer 5

The speed of a moving object can be calculated from the gradient of the line on a distance-time graph:

Question 6

What is the speed of an object?

Answer 6

The speed of an object is the distance it travels every second
Speed is a scalar quantity
This is because it only contains a magnitude

Question 7

How is Average speed calculated?

Answer 7

Average speed = distance moved / time taken

Question 8

Explain the aim of Core practical 1: Investigating motion

Answer 8

The aim of this experiment is to investigate the motion of some everyday objects, such as:
A paper cone
A tennis ball
This is just one method of carrying out this experiment - some methods involve the use of light gates to measure speed and acceleration, e.g. for a toy car moving down a slope
Variables:
Independent variable = Distance, d
Dependent variable = Time, t
Control variables:
Use the same object (paper cone, tennis ball etc.) for each measurement

Question 9

What is the apparatus used for this experiment?

Answer 9

Question 10

What is the method for Core practical 1?

Answer 10

Measure out a height of 1.0 m using the tape measure or metre ruler
Drop the object (paper cone or tennis ball) from this height, which is the distance travelled by the object
Use the stop clock to measure how long the object takes to travel this distance
Record the distance travelled and time taken
Repeat steps 2-3 three times, calculating an average time taken for the object to fall a certain distance
Repeat steps 1-4 for heights of 1.2 m, 1.4 m, 1.6 m, and 1.8 m

Question 11

What is the analysis of this result?

Answer 11

Therefore, calculate the average speed at each distance by dividing the distance by the average time taken

Question 12

What is the evaluation of this experiment?

Answer 12

Systematic Errors:

Make sure the measurements on the tape measure or metre rule are taken at eye level to avoid parallax error
Consider using an electronic sensor, such as light gates, to obtain highly accurate measurements of time
Once the object is released, the timer starts and stops automatically as it reaches the sensor on the ground
Random Errors:
Ensure the experiment is done in a space with no draught or breeze, as this could affect the motion of the falling object
Using a ball bearing and an electronic data logger, like a trap door, is a good way to remove the error due to human reaction time for this experiment
Safety Considerations
Place a mat or a soft material below any falling object to cushion its fall

Question 13

What is acceleration?

Answer 13

Acceleration is defined as the rate of change of velocity
In other words, it describes how much an object’s velocity changes every second

Question 14

What is the eq. for acceleration?

Answer 14

Acceleration = Change in velocity/ Time taken

Question 15

What is the change in velocity?

Answer 15

The change in velocity is found by the difference between the initial and final velocity, as written below:
change in velocity = final velocity − initial velocity

Δv = v − u
v = final velocity in metres per second (m/s)
u = initial velocity in metres per second (m/s)

Question 16

What is the speeding up and slowing down of an object?

Answer 16

An object that speeds up is accelerating
An object that slows down is decelerating
The acceleration of an object can be positive or negative, depending on whether the object is speeding up or slowing down
If an object is speeding up, its acceleration is positive
If an object is slowing down, its acceleration is negative (sometimes called deceleration)

Question 17

What is a velocity time graph?

Answer 17

A velocity-time graph shows how the velocity of a moving object varies with time
The red line represents an object with increasing velocity
The green line represents an object with decreasing velocity

Question 18

How is acceleration represented on a velocity time graph?

Answer 18

Velocity-time graphs also show the following information:
If the object is moving with a constant acceleration/deceleration
The magnitude of the acceleration/deceleration
A straight line represents constant acceleration
The slope of the line represents the magnitude of acceleration
A steep slope means large acceleration (or deceleration) - i.e. the object’s speed changes very quickly
A gentle slope means small acceleration (or deceleration) - i.e. the object’s speed changes very gradually
A flat line means the acceleration is zero - i.e. the object is moving with a constant velocity

Question 19

How can acceleration of an object can be calculated from the gradient of a velocity time graph?

Answer 19

Acceleration = Gradient = rise/run

Question 20

What is the displacement of a graph?

Answer 20

The area under a velocity-time graph represents the displacement (or distance travelled) by an object

Question 21

How can the area of the graph be calculated if it is a triangle?

Answer 21

Area = ½ × Base × Height

Question 22

How can the area of the graph be calculated if it is a rectangle?

Answer 22

Area = Base × Height

Question 23

How can the distance from a velocity of a time graph?

Answer 23

Enclosed areas under velocity-time graphs represent total displacement
If an object moves with constant acceleration, its velocity-time graph will comprise of straight lines
In this case, calculate the distance travelled by working out the area of enclosed rectangles and triangles as in the image above

Question 24

How is uniform acceleration calculated?

Answer 24

The following equation of motion applies to objects moving with uniform (constant) acceleration:
(final speed)2 = (initial speed)2 + 2 × acceleration × distance moved

v2 = u2 + 2as

Where:
s = distance moved in metres (m)
u = initial speed in metres per second (m/s)
v = final speed in metres per second (m/s)
a = acceleration in metres per second squared (m/s2)
This equation is used to calculate quantities such as initial or final speed, acceleration, or distance moved in cases where the time taken is not known