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Physics IB > Chapter 2 - Mechanics > Flashcards

Chapter 2 - Mechanics Flashcards

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1
Q

What is an instantaneous value?

A

It’s a value at one particular time

Instantaneous speed is also the same as velocity

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2
Q

How do you work out relative velocities?

A

By Simple addition or subtraction as appropriate.

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3
Q

Features of a displacement-time graph

A

The gradient is equal to the velocity

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4
Q

Features of a velocity-time graph

A

The gradient is equal to the acceleration

The area under the graph is the displacement

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5
Q

Features in a Acceleration-time graph

A

The area under the graph is the change in velocity

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6
Q

How do you use light gates to measure acceleration?

A

It’s a device that senses and records the time of when an object cuts through a beam of light. Use the length of the object that breaks the beam, the average speed can be calculated.

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7
Q

How do you use strobe photography to measure acceleration?

A

It gives out brief flashes of light at fixed time intervals. Use the camera and if it’s the only source of light, pictures will have captured the objects motion.

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8
Q

How do you use ticker timer to measure acceleration?

A

It has dots on a strip of paper at regular time intervals. (Normally every 1/5 of a second). Attach it to the object and let it fall. The length of the paper and time are then used.

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9
Q

What is the condition needed to use the SUVAT equations?

A

Constant acceleration

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10
Q

What does the U and the V stand for in the SUVAT equations?

A

U - initial velocity

V - final velocity

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11
Q

What does it mean if an objects in free-fall?

A

When we can ignore the effects of air resistance and the object is falling in a uniform gravitational field.

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12
Q

What’s the shape of projectile motion?

A

Parabola

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13
Q

What are the only forces acting during a projectile motion?

A

Gravity and friction. In many situations air resistance can be ignored

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14
Q

What are the components of projectile motion?

A

The vertical and horizontal motion are independent of one another - assuming the gravitational force is constant.

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15
Q

Horizontal component to projectile motion?

A

There are no forces in this direction, there is no horizontal acceleration. So the velocity in this direction must be constant

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16
Q

Vertical component in projectile motion

A

There’s a constant vertical force downwards of 9.81/ 10 ms^-2,
so there is constant vertical acceleration.

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17
Q

What’s the method to solve any problem of projectile motion?

A

1) . Use angle of launch to resolve initial velocity into components
2) . Use vertical component of velocity to determine time of flight
3) . Use the horizontal component and time of flight for the range
4) . Use vector addition to solve for velocity at any point

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18
Q

If there is a given speed, what angle of launch is needed for the greatest range?

A

45 degrees

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19
Q

What will happen if 2 objects are released together, one from rest and the other one already with a horizontal velocity?

A

They will both hit the ground together because the forces pulling them down are the same.

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20
Q

What happens when an object moves through a fluid?

A

There will be frictional fluid resistance e.g terminal velocity
It can also be called viscous drag

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21
Q

What factors effect the drag force on an object?

A

Relative velocity of the object with respect to the fluid
Shape and size of the object
The fluid used

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22
Q

What happens to the projectile motion of an object when fluid resistance is taken into account?

A

The vertical and horizontal components of velocity will both be reduced, thus the path the object takes will be smaller.

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23
Q

What is force?

A

The cause of a deformation or a velocity change

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24
Q

What’s the effect of a resultant force?

A

A change in velocity, thus acceleration.

If the resultant force is zero then velocity is constant

25
Q

To describe a force, on must include….

A 
magnitude 
Direction 
The object on which it reacts 
The object exerting the force 
Nature of the force
26
Q

What are all the different types of forces?

A

Gravitational, electrostatic, magnetic, normal reaction, friction, tension, compression, upthrust and lift.

27
Q

Hooke’s law

A

Up to the elastic limit, the extension ‘X’ of a spring is proportional to the tension force F.
The constant of proportionality is K - spring constant.

28
Q

Forces as vectors

A

Forces can be split up into components

29
Q

Free-body diagrams

A

One object ONLY is chosen

All the forces acting on that object are shown and labelled

30
Q

Newton’s first law

A

An object continues in a uniform motion in a straight line or at rest unless a resultant external force acts

31
Q

When does Translational equilibrium occur?

A

When the resultant force is zero (in any direction)

It doesn’t mean the same as being at rest

32
Q

What is tension?

A

When a spring/string is stretched, it has equal and opposite forces on its ends pulling outwards.
It’s the force that the end of the string applies to another object.

33
Q

What is Newton’s second law?

A

A resultant force causes an acceleration

34
Q

What is Newton’s second law in terms of momentum?

A

The resultant force is proportional to the rate of change of momentum

35
Q

Equation for resultant force

A

F = 🔼p / 🔼t

36
Q

Equation for force and the condition needed?

A

F = m x a
It only applies if we use SI units
If there are several forces acting on an object then work out the resultant force first and then apply the law.

37
Q

The method used to find the resultant force when friction is involved.

A

The resultant force = forward force - friction

38
Q

Newton’s third law

A

When two bodies A and B interact, the force that A exerts onto B is equal and opposite to the force that B exerts into A

39
Q

2 Key points about Newton’s third law:

A

Equal and opposite forces that act on the same object are not Newton’s third law pairs
The forces must also be the same type

40
Q

How does size of mass influence velocity gained?

A

The smaller mass will gain the greater velocity

The mass of some objects are so large that the force on it doesn’t cause any acceleration.

41
Q

What’s the difference between mass and weight?

A

Mass is the amount of matter contained in an object

Weight is the gravitational force on an object

42
Q

What is the equation for gravitational force and what’s the value of g on the moon?

A

Gravitational force = m x g

g on the moon = 1.6 N kg^-1

43
Q

What’s the definition of work done and it’s units?

A

The amount of energy transferred is equal to the work done.

Unit of work done is joules, j

44
Q

What’s the conservation of energy?

A

Energy is neither created or destroyed it just changes form

45
Q

What are the 12 types of energy?

A

Kinetic, Gravitational potential, Elastic potential, Electrostatic potential, Radiant, Thermal, Nuclear, Solar, Chemical, Electrical, Internal and Light

46
Q

Equation for K.E

A

K.E = 1/2 mv^2

47
Q

Equation for G.P.E

A

G.P.E = mgh

48
Q

Equation for elastic potential energy

A

Elastic potential energy = 1/2 k 🔼x^2

k = Spring constant in NM^-1 
🔼x = the extension
49
Q

Definition of power

A

The rate at which energy is transferred

50
Q

Equation for power and its units

A

Power = energy transferred ( work done) / time taken

SI unit for power = Js^-1 or W (watts)

51
Q

Equation for efficiency

A

Efficiency = useful energy out / total energy in

52
Q

Equation for momentum and its units

A

Momentum = mass x velocity
Units: Kg ms^-1
It’s a vector

53
Q

Definition of impulse and its equation

A

Impulse is the change in momentum

🔼p = F x 🔼t

54
Q

What is the important feature of a force time graph?

A

The area under the graph is the total impulse

55
Q

What’s the convention of momentum?

A

The total linear momentum of a system of interaction particles remains constant provided there is no resultant external force.

56
Q

What is an elastic collision?

A

It’s a collision where no mechanical energy is lost. Relative velocity is the same before and after.
In reality collisions do lose some energy

57
Q

What’s a totally inelastic collision?

A

A large amount of mechanical energy is lost but total momentum stays the same. (The objects start moving together)

There’s no relative velocity in this case because they aren’t compared against each other as they’re moving together

58
Q

What’s an inelastic collision?

A

Some energy is lost but the objects don’t carry on moving together. Most likely in an real life situation.

Physics IB (7 decks)

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