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AS Level CIE physics > Kinematics > Flashcards

Kinematics Flashcards

1
Q

Define distance:

A

Distance “d” is the the total length covered by an object between two points. It is a scalar quantity. The SI unit is meter (m).

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2
Q

Define displacement:

A

Displacement “s” is the shortest distance between any two points or distance in a specified direction. It is a vector quantity. SI unit is meter (m).

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3
Q

Define Speed:

A

Speed is the total distance travelled per unit of time or rate of change of distance. It is a scalar quantity. v=d/t. hence speed’s unit is (m/s).

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4
Q

Define average speed:

A

Average speed (Vav) is the total distance travelled divided by total time taken.

Vav= V+U/2

where u=Initial speed/Velocity and V=Final Speed/Velocity

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5
Q

Define velocity:

A

Velocity is the rate of change of displacement of an object OR displacement per unit time. It is a vector quantity.

V=s/t = Δs/Δt = ds/dt

measured in m/s

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6
Q

Define average velocity:

A

Average Velocity (Vav) is the total displacement divided by total time taken.

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7
Q

Define uniform velocity:

A

Uniform velocity means Rate of change of displacement is constant. There is no change in magnitude or direction of velocity.

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8
Q

Define acceleration:

A

Acceleration is defined as the rate of change of velocity of an object.

a=v-u/t

(m/s^2)

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9
Q

Define uniform acceleration:

A

Uniform acceleration means rate of change of velocity is constant.

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10
Q

What is the first equation of motion?

A

v=u+at

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11
Q

What is the second equation of motion?

A

s=ut + 1/2at^2

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12
Q

What is the third equation of motion?

A

v^2-u^2=2as

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13
Q

What is the value of acceleration due to gravity?

A

9.81

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14
Q

Define thinking distance:

A

Thinking distance is the distance travelled by the car during the reaction time of the driver before he applies the brakes. We assume speed and reaction time remains constant.

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15
Q

Define breaking distance:

A

Breaking distance is the distance travelled by the car when the brakes are applied and the car comes to rest. Deceleration of the car remains constant.

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16
Q

What is the thinking distance formula?

A

S1= U x T
where t=reaction time and u=Initial velocity

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17
Q

What is the relationship between thinking distance and initial velocity?

A

S1 ∝ U

(directly proportional)

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18
Q

What are the factors affecting thinking distance/reaction time?

A

Driver is not alert/Use of mobile
Intoxication/Drowsiness
Age factor/Eyesight/Fog/Unclear vision

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19
Q

What is the braking distance formula?

A

v^2-u^2 = 2as
-u^2= 2 (-a) s
-s=u^2/2a

where u=initial velocity v=final velocity and a=deceleration

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20
Q

what is the relationship between braking distance and initial velocity?

A

S ∝ U^2

s is directly proportional to initial velocity

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21
Q

What are the factors affecting braking distance?

A

1.Wet road conditions (less friction, less deceleration)
2.Worn out tires (less friction)
3.Old/Faulty breaking system
4.Overloading of car/Inertia (f=ma) (higher kinetic energy)

22
Q

Define Fluid Friction:

A

Fluid Friction is the resistance that opposes an object’s motion in a fluid (liquid and gas).

23
Q

What are the factors which affect fluid friction?

A

Fluid Friction depends upon:
* Shape of the object
* Density of the fluid (viscosity)
* Speed of the object
* Temperature
* Pressure

24
Q

Explain the affect of viscosity on fluid friction.

A

Fluids with high viscosity offer more resistance than the ones with low viscosity.

25
Q

Explain the affect of the speed of the object on fluid friction.

A

Frictional forces increases with the speed of the object.

26
Q

Explain the affect of temperature on fluid friction.

A

As the temperature increases, the viscosity of liquids decreases, whereas the viscosity of gases increases.

27
Q

Explain the affect of pressure on fluid friction.

A

With an increase in pressure, the viscosity of liquids increases, except water. The viscosity of gases is unaffected.

28
Q

What are the forces experienced by an object moving in a fluid?

A

If an object moves in a fluid like air, it experiences the following forces:
Weight
Air resistance
Up-thrust

29
Q

Explain the affect of the forces weight and up-thrust on an object moving in a fluid.

A

Weight and up-thrust are constant forces.

30
Q

Explain the affect of the force air resistance on an object moving in a fluid.

A

Air resistance increases with velocity. The direction of air resistance is always opposite to motion of the object.

31
Q

Explain the events that occur when an object is falling.

A

Initially, weight>air resistance+upthrust, thus there is a net downward force. Due to this force the object will start to accelerate.

As the object accelerates velocity increases and this increases the air resistance. Thus the resultant downward force starts to decrease.

A stage comes when weight=air resistence+upthrust. Now there is zero resultant force acting on the object, so the object starts to move with maximum constant velocity called “terminal velocity”.

32
Q

Define terminal velocity:

A

Terminal Velocity is the maximum velocity an object attains.

33
Q

What are contact forces?

A

Contact forces are forces that act between the objects when the objects are in contact with each other.

34
Q

State Newton’s first law of motion:

A

Every body continues in its state of rest or uniform motion in a straight line, unless acted upon by a net or resultant force.

It is also called law of inertia.

35
Q

Define Inertia

A

Inertia is the property of an object to resist any change in state of rest or uniform motion in a straight line.

inertia is directly proportional to the mass of an object.

36
Q

How is resultant force calculated?

A

Resultant force=Forward Force-Resistive Force.

37
Q

Define resultant force:

A

The resultant force is a single force that has the same effect as two or more forces acting together.

38
Q

What happens when forward force is greater than resistive force?

A

if forward force is greater than resistive force than object will accelerate as the resultant force is equal to forward force- resistive force.

39
Q

What happens when Forward force is less than resistive force?

A

When forward force is less than resistive force then the object will decelerate as resultant force is equal to forward force-resistive force.

40
Q

What happens when forward force=resistive force?

A

When forward force is equal to resistive force than either the object remains at rest OR moves with constant speed/Velocity.

41
Q

What is the normal force?

A

The normal force is the push that a surface (or object) exerts back on an object that comes into contact with it. It is a contact force. The normal force always acts perpendicular to, and away from the surface.

42
Q

Define momentum:

A

Momentum (p) of a body is defines as the product of mass (m) and velocity. Momentum is a vector quantity therefore it has direction.
Therefore momentum of an object will change if:
* The object accelerates (speeds up) or decelerates (slows down).
* Changes direction
* Its mass changes

43
Q

What are momentum’s units?

A

kg x m/s

44
Q

What is the formula for momentum?

A

Momentum= mass x velocity

P=mv

45
Q

Why can momentum be positive and negative?

A

Since velocity is a vector this means that the momentum of an object also depends on its direction of travel
This means that momentum can be either positive or negative.
If an object travelling to the right has positive momentum, an object travelling in the opposite direction (to the left) will have negative momentum

46
Q

Define Mass

A

Mass is a measure of the inertia of an object to change in velocity. Mass will resist changes in motion. The bigger the mass the more difficult it is to change its state of rest or velocity . The SI unit for mass is kilogram (kg).

47
Q

Define weight

A

Weight is the effect of a gravitational field on a mass. The weight of a body is equal to the product of its mass (m) and the acceleration of free fall (g).

w=mg

48
Q

What is weight measured in?

A

Since weight is a force of an object due to the pull of gravity, it is measured in newton’s (N) and is vector quantity with both magnitude and direction.

49
Q

Define newtons second law of motion.

A

A resultant force acting on a body will cause a change in momentum or direction of the force. The rate of change of momentum is directly proportional to the magnitude of the force. This can only be written as F=ma.

50
Q

Derive the formula of force from newtons second law.

A

force= change of momentum with change of time. F=d(mv)/dt.

force=change in mass x velocity with time.

force=mass x acceleration.

51
Q

What is the definition of force?

A

Force is defined as the rate of change of momentum.

AS Level CIE physics (8 decks)

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