Topic 2 - Motion And Forces COPY Flashcards

1
Q

What is a vector quantity?

A

Vectors have magnitude and direction

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2
Q

Give examples of vector quantities.(6)

A

Forces, velocity, displacement, weight, acceleration, momentum, etc.

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3
Q

What are scalar quantities?

A

Scalar quantities only have magnitude and no direction.

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4
Q

Give example of scalar quantities. (6)

A

Speed, distance, mass, energy, temperature, time, etc.

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5
Q

What is displacement?

A

Displacement is a vector quantity which measures the distance and the direction in a straight line form the starting point to the finishing point.

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6
Q

How is velocity different from speed?

A

Velocity is speed in a given direction.

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7
Q

What is the formula for average speed?

A

Average speed (m/s)= distance (m) / time (s)

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8
Q

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

A

Speed of an object.

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9
Q

Recall typical speeds of these:

  • Wind
  • Sound in air
  • Person walking
  • Person running
  • Cyclist
  • Car driving through town
  • Car driving on Motorway
  • Train
A
  • Wind - 6m/s
  • Sound in the air - 340m/s
  • Person walking - 1 m/s
  • Person running - 3 m/s
  • Cyclist- 5.5 m/s
  • Car driving through town - 13 m/s
  • Car on Motorway - 30 m/s
  • Train - 45 m/s
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10
Q

List two equations to work out acceleration.

A

Acceleration (m/s2)= (V - U) / T (Secs)

v2 - u2 = 2 X a (m/s2) X x(metre)

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11
Q

What does a diagonal line (/) represent on a distance-time graph?

A

Moving slowly/quickly (depending on the gradient) at a constant speed.

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12
Q

How do you calculate speed or distance on a point on a curved line on a distance-time graph?

A

Draw tangent to the curve at the point.

Then calculate the gradient of the tangent

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13
Q

What is uniform acceleration also known as?

A

Constant acceleration

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14
Q

What does a -acceleration mean?

A

Deceleration

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15
Q

What does the flat along 0 for the time axis mean (velocity-time graph)?

A

Stationary

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16
Q

How do you work out acceleration from a velocity-time graph?

A

Acceleration = Gradient of velocity-time graph

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17
Q

What does a diagonal line mean on a velocity-time graph?

A

Constant acceleration

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18
Q

Why does a object moving in a circular motion have a changing velocity?

A
  • When an object moves in a circle at a constant speed, its direction constantly changes.
  • A change in direction causes a change in velocity - This is because velocity is a vector quantity – it has an associated direction as well as a magnitude.
  • A change in velocity results in acceleration, so an object moving in a circle is accelerating even though its speed may be constant.
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19
Q

Why must there be a centripetal force for circular motion?

A
  • An object will only accelerate if a resultant force acts on it.
  • For an object moving in a circle, this resultant force is the centripetal force that acts towards the middle of the circle.
20
Q

Formula for weight (N)

A

Weight (N) = Mass (kg) x gravitational field strength (n/kg)

21
Q

What is weight measured in?

A

Newtons

22
Q

Describe the relationship between the weight of a body and the gravitational field strength

A
  • Weight is the result of gravity. The gravitational field strength of the Earth is 10 N/kg (ten newtons per kilogram).
  • This means an object with a mass of 1kg would be attracted towards the centre of the Earth by a force of 10N.
  • We feel forces like this as weight.
23
Q

What is Newton’s second law?

A

The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.

This means that F = M x A

24
Q

What is inertial mass?

A

The ratio of force over acceleration is called inertial mass.
Inertial mass is a measure of how difficult it is to change the velocity of an object.

25
Q

What is Newton’s third law?

A

For every action, there is an equal and opposite reaction.

26
Q

What is Newton’s first law?

A

If there is no forces acting on a body (or the forces acting on it are balanced) the object will continue to do what is it is already doing.

  • if the object is stationary, it will remain
  • if the object is moving, it will continue to move at the same speed and in the same direction
27
Q

Describe the Core Practical : Investigate the relationship between force, mass and acceleration by varying the masses added to trolleys

A
  • By releasing masses over the side of the bench a force will be applied to the trolley, causing it to accelerate down the ramp.
  • Light gates can be positioned along the ramp to measure the velocity of the trolley at different points and record the time between these measurements.
  • Different number of masses can be added to the trolley.
28
Q

How do you find the distance travelled on a velocity-time graph?

A

Work out area under the line on the graph and above the horizontal axis.

29
Q

How do you work out momentum?

A

Momentum (Kgm/s) = Mass (kg) x Velocity (m/s)

30
Q

Which six factors affects stopping distance?

A
  • Mass of Vehicle
  • Speed of Vehicle
  • Driver’s reaction time
  • State of Vehicle’s brakes
  • State of the road
  • Amount of friction between tyre and road surface
31
Q

How do you work out the stopping distance?

A

Thinking distance + Braking distance

32
Q

What factors affect Driver’s reaction times?

A
  • Age
  • Gender
  • Physical fitness
  • Fatigue
  • Distraction
  • Alcohol
33
Q

How do you work out force using momentum?

A

Force (N) = change in momentum (kgm/s) / time (s)

34
Q

Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds

A
20 mph - 12m
30 mph - 23m
40 mph - 36m
50 mph - 53m
60 mph - 73m
70 mph - 96m
35
Q

What does a flat line on a velocity-time graph represent?

A

Constant velocity

36
Q

How does Newton’s third law connect to equilibrium situations?

A
  • It applies in static (non-moving) situations, such as a book resting on a table.
  • This is where the force from the weight of book and the reaction from the table is equal therefore cancelling out so it doesn’t move.
37
Q

What is the acceleration in free fall?

A

10m/s2

38
Q

How does Newton’a third law apply to car collisions?

A
  • Newton’s Third Law of Motion applies in collisions, such as a car crashing into a tree.
  • The car and tree exert equal and opposite forces on each other in the collision.
  • When two objects collide the total momentum before the collision is equal to the total momentum in the absence of external forces.
  • This is the law of conservation of momentum, it is true for all collisions.
39
Q

What does a curved line going upwards represent?

A

Acceleration

40
Q

How do you work out ‘Work Done’?

A

Work done = Energy transferred

Work (Joules) = Force (Newtons) x Distance moved in direction of force (metres)

41
Q

What does a flat line on a distance-time graph represent?

A

Not moving/stationary

42
Q

How do you work out ‘Kinetic Energy’?

A

Kinetic Energy = 1/2 x mass x velocity squared

43
Q

What does Kinetic Energy equal when stopping a car?

A

KE = Work done

1/2 x mass x velocity squared = Force (applied by brakes) x Braking distance.

44
Q

Why are large decelerations bad?

A
  • When there is a car crash, the car, its contents and the passengers decelerate rapidly.
  • They experience great forces because of the change in momentum which can cause injuries.
45
Q

What safety features are implemented into cars to reduce injury from large decelerations?

A

Modern cars have safety features that absorb kinetic energy in collisions. These typically include:

  • seat belts
  • air bags
  • crumple zones
46
Q

How do safety features in a car prevent injury to the occupants?

A
  • These features reduce injuries to the people in the car by absorbing energy from the impact.
  • They increase the time taken for the change in momentum on the occupants’ bodies, and so reduce the forces involved and any subsequent injuries.