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A Level Physics > 02 - Mechanics > Flashcards

02 - Mechanics Flashcards

1
Q

What must always be true when using the SUVAT equations of motion?

A

The acceleration must be uniform - if the acceleration is changing, the equations are not valid.

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2
Q

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

A

Speed

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3
Q

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

A

Velocity

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4
Q

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

A

Acceleration

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5
Q

Describe the shape of a velocity-time graph for an object travelling with uniform acceleration.

A

If acceleration is constant, the gradient of the velocity-time graph will be constant and so it will form a straight line graph.

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6
Q

Describe the shape of a velocity-time graph for an object travelling with non-uniform acceleration.

A

If acceleration is not constant, the gradient of the velocity-time graph will change and so it will form a curve.

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7
Q

Compare the velocity-time graphs for a uniformly accelerating and a uniformly decelerating object.

A

• For an accelerating object, the gradient will be positive
• For a decelerating object, the gradient will be negative

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8
Q

What is a scalar quantity

A

A scalar quantity is one that has a magnitude but not a fixed direction.

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9
Q

What is a vector quantity?

A

A vector quantity is one that has a magnitude and a fixed direction.

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10
Q

Give five examples of scalar quantities.

A
  1. Distance
  2. Speed
  3. Mass
  4. Energy
  5. Temperature
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11
Q

Give five examples of vector quantities.

A
  1. Displacement
  2. Velocity
  3. Acceleration
  4. Momentum
  5. Force
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12
Q

How is a vector quantity represented on a diagram?

A

• As an arrow
• The direction of the arrow represents the direction of the quantity
• The length of the arrow represents the magnitude of the quantity

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13
Q

What does resolving a vector involve?

A

Splitting the vector into two perpendicular components (vertical and horizontal

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14
Q

How should the components of a proiectile be handled when carrying out calculations?

A

• The horizontal and vertical components are independent of each other and so should be treated separately
• SUVAT should be used separately for each component

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15
Q

If a projectile is moving freely under gravity, what can be said about the vertical acceleration?

A

The vertical acceleration will be the acceleration due to gravity and so will have a magnitude of 9.81 ms.

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16
Q

On a displacement/time graph what does a curve in the graph represent

A

Acceleration/deceleration

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17
Q

What does the area under the graph of a velocity/ time graph represent

A

Displacement

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18
Q

Which suvat equation would you use if u had : v , t , u and a

A

V = u + at

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19
Q

Which suvat equation would you use if u had : a , t , u and s

A

S = ut + 1/2at^2

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20
Q

Which suvat equation would you use if u had : u, v, a and s

A

v^2 = u^2 + 2as

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21
Q

Which suvat equation would you use if u had : s, u, v, t

A

S = 1/2(u + v) t

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22
Q

What does u stand for in the suvat equations

A

Initial velocity

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23
Q

What does the v stand for in the suvat equations

A

Final velocity

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24
Q

What are the 4 suvat equations

A

v = u+at
S = ut + 1/2at^2
v^2 = u^2 + 2as
S = 1/2 (u+v)t

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25
Q

State Newton’s first law

A

An object will continue to move with uniform velocity, unless it is acted on by resultant external force

26
Q

What is newton’s second law?

A

F = ma
Only uses when the object experiences a resultant force (is accelerating or decelerating)

27
Q

Can an object travelling with constant speed change direction, without an external force acting?

A

For an object to change direction, its velocity must change. This means there must be an acceleration. An acceleration cannot occur without an external resultant force acting.

28
Q

Describe the forces acting on an object travelling at terminal velocity.

A

• The forces are balanced in both the vertical and horizontal components of its motion
• There is no resultant force, and therefore no acceleration

29
Q

What is meant by terminal velocity?

A

For a given set of conditions, the terminal velocity is the maximum speed of the object. An object has zero acceleration at terminal velocity.

30
Q

State the equation used to calculate the weight of an object.

A

W = mg
Weight = Mass x Gravitational Field
Strength

31
Q

State Newton’s third law

A

Every action has an equal and opposite reaction

32
Q

Describe in Newton’s third law pair of someone holding a mass

A

There is a normal contact force of it on you, and you are exerting a normal contact force on it

33
Q

What are the conditions for Newton’s third law?

A

Equal in magnitude
Acting in opposite directions
The same type of force
Acting on different objects

34
Q

When talking about Newton’s third law, what would you describe weight as

A

Weight is a gravitational force

35
Q

What is the Newton’s third law pair of someone standing on Earth?

A

The gravitational force of the person on the Earth, and the gravitational force of the Earth on the person

36
Q

State the equation for momentum.

A

p = mv
Momentum = Mass x Velocity

37
Q

What is the unit of momentum?

A

kgms^-1

38
Q

What is the consequence of the linear conservation of momentum?

A

The total momentum of a system before an event is always equal to the total momentum of the system after the event.

39
Q

What is the law of the conservation of energy?

A

Energy cannot be created or destroyed, only transferred from one energy store to another

40
Q

State the equation used to calculate the work done by a force.

A

W = F x s
Work Done = Force × Change in
Distance

41
Q

What force is used when calculating the work done by a force over a distance?

A

The component of the force that is in the direction of the object’s motion.

42
Q

What is the unit of work?

A

Joules, J

43
Q

What is the work done by the force, F when it moves the object a distance of x? When F is at an angle

A

You work out the horizontal component so:

Work Done = Fcos(angle)x

44
Q

What form of energy do all moving objects have?

A

All moving objects have kinetic energy.

45
Q

State the equation used to calculate the kinetic energy of an object.

A

Kinetic Energy = ½ × Mass × Velocity^2
E = ½ mv^2

46
Q

What form of energy does a raised object have?

A

Gravitational Potential Energy

47
Q

State the equation used to calculate gravitational potential energy.

A

GPE = Mass × Gravitational Field
Strength x Height
E = mgh

48
Q

What is power?

A

The rate at which energy or work is
done.

49
Q

State 3 equations used to calculate power.

A

P= E/ t
P = Work done / time
P = force x velocity

50
Q

What is the unit of power?

A

Watt, W

51
Q

State the equation relating energy and efficiency.

A

Efficiency =
Useful Energy Output / Total Energy Input

52
Q

State the equation relating power and efficiency.

A

Efficiency =
Useful Power Output / Total Power Input

53
Q

What is the unit of efficiency?

A

Efficiency is a ratio and so doesn’t have an associated unit.

54
Q

What is a moment?

A

A moment is the turning effect of a force.

55
Q

State the equation used to calculate the moment of a force.

A

Moment of a Force = Force × Distance

56
Q

What distance must be used when calculating a moment?

A

The perpendicular distance between the line of action of the force and the axis of rotation.

57
Q

What is the unit of a moment?

A

Nm

58
Q

What is the principle of moments?

A

For an object to be in equilibrium, the sum of the clockwise moments about a point must be equal to the sum of the anticlockwise moments.

59
Q

What is an object’s centre of gravity?

A

The single point through which the object’s entire weight can be said to act.

60
Q

How would you carry out an experiment working out the centre of gravity of an object

A

Punch 3 holes in each corner of the object.
Attach a hanging mass to a needle and put it in a bung which is being held by a clamp stand.
Draw a line from which the string/hanging mass goes over. Repeat for each hole. The point where all the lines cross is the centre of gravity

61
Q

What will occur if the line of action an object’s centre of gravity lies outside its base?

A

The object’s weight will produce a resultant moment and so if is unsupported, the object may topple.

62
Q

What is an elastic in an inelastic collision

A

Elastic- all kinetic energy and momentum is conserved
Inelastic - some energy and momentum is lost

A Level Physics (6 decks)

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