Motion

Question 1

State the word equation for average speed

Answer 1

• average speed = distance travelled / time taken

Question 10

State the symbol equation for average speed

Answer 10

• v = delta x / delta t

Answer 11

• Graphs of distance against time are used to represent the motto of objects

Answer 13

• Distance is plotted on the y-axis
• Time is plotted on the x-axis

Answer 14

• In a d-t graph, a stationary object is represented by a horizontal straight line
• An object moving at a constant speed is represented by a straight, sloping line
• The gradient of that line is equal to the the speed of the object

Question 15

Define instantaneous speed

Answer 15

• The speed of the car over a very short interval of time

Question 16

How is the instantaneous speed of a particular time found?

Answer 16

• By drawing the tangent to a d-t graph then determining the gradient of the tangent
• The greater the gradient, the greater the instantaneous speed

Question 17

What is the direction of instantaneous velocity?

Answer 17

• Tangential to the path

Question 18

Describe displacement

Answer 18

• vector quantity with magnifier and direction

Question 19

Describe distance

Answer 19

• Scalar quantity,

Question 20

How is speed calculated

Answer 20

• Speed is scalar quantity calculated from distance

Answer 21

• Velocity is a vector quantity calcuetd from displacvtemtn

Question 22

State the word equation for average velocity

Answer 22

• average velocity = change in displacement / time taken

Question 23

State the symbol equation for average velocity

Answer 23

v = delta s / delta t

Answer 24

• graphs of displacement against time are used to represent the motion of objects

Answer 25

• Displacement is plotted on the y axis
• Time is plotted on the x axis

Answer 26

• If a car is travelling at a constant velocity, the line is sloping upwards
• For the displacement of the car remains constant, it is horizontal, therefore the car must be stationary
  If there is a negative slow, the displacement of the car is getting smaller with time, car must be retiring to a constantly velocity

Answer 27

• You can determine the velocity of an object from the gradient
• If not a straight line draw a tangent to determine instant velocity

Question 28

Define acceleration

Answer 28

• Rate of change of velocity

Question 29

State the word equation for acceleration

Answer 29

• acceleration = change in velocity / change in time

Question 30

State the symbol equation for acceleration

Answer 30

• a = delta v / delta t

Question 31

State the unit of acceleration

Answer 31

ms-2

Question 32

What is a negative acceleration often called?

Answer 32

• deceleration

Question 33

Is acceleration a scalar or vector quantity?

Answer 33

• Determined from velocity, therefore vector
• Has magnitude and direction

Answer 34

• in a velocity time graph - y axis represents velocity

Answer 35

• acceleration = gradient of velocity time graph

Answer 36

• A straight line of constant positive gradient = constant acceleration
• straight line of zero gradient= constant velocity or zero acceleration
• a straight line of constant negative gradient : constant deceleration
• curve with a changing gradient : accerleration is changing

Answer 37

• Tachographs record the speed and distance travelled by a vehicle

Answer 38

• change in displacement to equal to area under the graph

Answer 39

• when acceleration is constant, displacement is easy to calculate because the areas can be broken down into rectangles and right angle triangles

Answer 40

• for non linear velocity time graphs you cam determine the area under the graph by counting squares

Answer 41

• need four equations to calculate quantities involving motion in a straight line at a constant acceleration (SUVAT)

Question 42

velocity time graph equations from the graph

Answer 42

Gradient = (v-u)/t
Area = 1/2 x (v-u) x t - rectangular area
area = u x t - triangular area

Question 43

state

Answer 43

v = u + at

Question 44

equation without v
substitute v-u = at into area of a triangle expression

Answer 44

s = ut +1/2at^2

Question 45

equation without a
if u treat area under graph as area of trapezium and use u and v as parallel side of trapezium and t as perpendicular separation

Answer 45

s = 1/2 (u+v)t

Question 46

equation without t

Answer 46

v2 = u2 + 2as

Question 47

how do u get v2 = u2 +2as

Answer 47

t = v-u / a
s = 1/2 (u+v) x (v-u) /a

Question 48

Define stopping distance

Answer 48

• The total distance travelled from when the driver first sees a reason to stop, to when the vehicle stops

Question 49

State the two components of stopping distances

Answer 49

• Thinking distance
• Braking distance

Question 50

Define thinking distance

Answer 50

• The distance travelled between the moment when you first see a reason to stop, the moment when you use the brake

Question 51

Define braking distance

Answer 51

• The distance travelled from the time the brake is applied until the vehicle stops

Question 52

State some factors that influence stopping distance

Answer 52

• Speed of vehicle
• The condition of brakes, tyres and roads
• Weather conditions
• Alertness of drivers

Question 53

State the word equation for thinking distance

Answer 53

• thinking distance = speed x reaction time

Answer 54

• The greater the speed or reaction time, the further a vehicle will travel before its drivers applies the brakes

Answer 55

• Assuming a constant the reaction time of 0.67s the thinking distance will be about 21m
  uk national speed limit of 70mph

Answer 56

in the uk Highway Code the braking distance at 30mph is shown as 14m
if you assume constant deceleration from 14.3 to 0 ms-1 you can use one of the equations of motion to determine the magnitude of the deceleration

Answer 57

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Question 58

3.7

Question 59

3.8