Module 3 Motion

Question 1

What is a scalar quantity?

Answer 1

one which has a magnitude but no direction (and a unit)

Question 2

What is a vector quantity?

Answer 2

one with a magnitude and direction (and a unit)

Question 3

How can scalar quantities be used in calculations?

Answer 3

normally, eg added, subtracted, multiplied, and divided in the normal manner

Remember scalar quantities can be negative

Question 4

Examples of vector quantities

Answer 4

Displacement
Velocity
Acceleration
Force
Momentum

Question 5

Examples of scalar quantities

Answer 5

Length
Mass
Speed
Time
Temperature
Volume
Potential difference
Power

Question 6

How can velocity be defined?

Answer 6

rate of change of displacement

Question 7

What is a resultant vector?

Answer 7

the value found when adding vectors in a vector addition

Resultant vector has magnitude and direction

Question 8

How to add parallel vectors

Answer 8

simply add them together to find the resultant vector

Question 9

What does “acting in the same line and direction” mean?

Answer 9

are parallel

Question 10

What is another word for vectors in opposite directions?

Answer 10

antiparallel

Question 11

How to add antiparallel vectors ie parallel vectors pointing in opposite directions?

Answer 11

one direction is considered positive the other negative and add them (assume right, or up is positive, and down or left is negative unless told otherwise)

Question 12

What are perpendicular vectors?

Answer 12

vectors acting at right angles to each other

Question 13

How to subtract vectors in opposite directions?

Answer 13

add them as you get a–b = a+b

Question 14

How to find resultant vector of perpendicular vectors?

Answer 14

at right angles so use Pythagoras
a^2 + b^2 = c^2

Question 15

How to find direction of resultant vectors

Answer 15

Use SOCAHTOA (trigonometry)

Question 16

Re angle of a vector - What does to the horizontal mean?

Answer 16

use the angle on the horizontal

Question 17

Re angle of a vector - What does to the vertical mean?

Answer 17

use the angle on the vertical

Question 18

What is resolving vectors?

Answer 18

splitting a resultant vector into two perpendicular components (vectors)

same as finding the components

Question 19

What is finding the components of a vector?

Answer 19

splitting a resultant vector into two perpendicular components (vectors)

same as resolving

Question 20

What are the two formulae used in resolving vectors?

Answer 20

Fcosθ to find the horizontal component (x-axis)

Fsinθ to find the vertical (y-axis)

angle is to the horizontal

Question 21

How to define speed?

Answer 21

rate of change of distance

Question 22

How to calculate average speed?

Answer 22

total distance travelled/time taken

Question 23

What does the gradient of a distance-time graph represent?

Answer 23

speed

Question 24

What is instantaneous speed?

Answer 24

the speed of an object over a very short interval of time

Question 25

How do you define velocity?

Answer 25

rate of change of displacement

Question 26

How to calculate average velocity?

Answer 26

change in displacement/time taken

Question 27

What is the symbol used for displacement?

Answer 27

s

Question 28

Why will the displacement of an object always be ≤ the distance?

Answer 28

displacement will be shortest route (as it is a straight line), distance will be actual distance

Question 29

What does the gradient of a displacement time graph represent?

Answer 29

velocity

Question 30

What does the area under a velocity time graph represent?

Answer 30

displacement of object

Question 31

How to calculate the displacement of under a velocity time graph with changing acceleration (ie curved graph)?

Answer 31

use the counting squares method Find the area of one small square (using your scale) Count the number of squares that are completely under the graph Add any squares that are over 50% under the graph Multiply the area of one square by number of squares

Question 32

How do you define acceleration?

Answer 32

rate of change of velocity

Question 33

What does deceleration represent?

Answer 33

negative acceleration (in the opposite direction of velocity)

Question 34

When looking at velocity-time graphs, what does a straight line with a positive gradient mean in terms of acceleration?

Answer 34

constant positive acceleration

Question 35

What does a horizontal line in a velocity-time graph represent in terms of acceleration?

Answer 35

constant velocity, zero acceleration

Question 36

What does a curve mean in terms of acceleration in a velocity time graph?

Answer 36

changing gradient therefore changing acceleration

Question 37

Define stopping distance?

Answer 37

total distance travelled from when a driver first sees the hazard and when the vehicle stops

Question 38

What is the thinking distance?

Answer 38

the distance travelled from the point between moment of first seeing the reason to stop and braking

Question 39

What is braking distance?

Answer 39

distance between applying brakes and the vehicle stopping

Question 40

How to calculate total stopping distance?

Answer 40

thinking distance+braking distance

Question 41

List 3 factors that effect stopping distance

Answer 41

Speed of the vehicle Conditions of the brakes, tyres and roads the weather conditions alertness of the driver

Question 42

How to calculate thinking distance?

Answer 42

speed of vehicle x reaction time

Question 43

What is the relationship between braking distance as the speed of a car?

Answer 43

distance proportional to u^2 from v^2=u^2 + 2as with v=0

Question 44

Explain the relationship between braking distance and speed (using KE)

Answer 44

When a car is travelling it has the KE=1/2mu^2 When it brakes it has the KE=braking force F x distance (formula for work done) If F, m, and 1/2 constant we can see that d ∝ u^2

Question 45

What is the effect on braking distance is speed is tripled?

Answer 45

d ∝ u^2 therefore distance increases by 3^2 = 9

Question 46

What information do you need to resolve a vector?

Answer 46

the magnitude and direction of a resultant vector