Physics - Forces & Motion Flashcards

1
Q

List the units and unit symbols for: mass, length, velocity, acceleration, force, time, gravitational field strength

A

Mass (kilogram, kg), length (metre, m), velocity (metre/second, m/s), acceleration (metre/second2, m/s2), force (Newton, N), time (second, s), gravitational field strength (newton/kilogram, N/kg)

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2
Q

List the units and unit symbols for: moments and momentum

A

Moments (newton metre, Nm), momentum (kilogram metre/second, m/s)

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3
Q

Plot a distance-time graph for the following motion: stationary, constant speed, acceleration, deceleration

A

SEE ONENOTE - IGCSE PHYSICS SUMMARY - 1b

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4
Q

Describe how speed can be determined from a distance-time graph

A

Use the gradient! =Δy/Δx= Change in distance/Change in time

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5
Q

Describe the motion of the lines on a distance-time graph above including total distance and speed

A

SEE ONENOTE
Red – constant speed starting at 2 m and finishing at 8 m. Total distance travelled in 2 s is 6 m. Speed is 3 m/s Blue – stationary at a distance of 4 m.
Yellow – deceleration starting at 0m and finishing at 6m. Total distance travelled in 2 s is 6 m.
Purple – acceleration starting at 0m and finishing at 6m. Total distance travelling in 2 s is 6 m.

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6
Q

Write down the equation relating average speed, change in distance and change in time in words and symbols

A

Average speed = Change in distance/Change in time

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7
Q

Write down another equation for average speed if acceleration is constant in words and symbols

A

Average speed = 1/2 (initial speed + final speed)

V_av = v+u/2

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8
Q

Describe a generic experiment to determine the average speed of an object

A

Describe/draw setup
Independent variable: State value of distance and how you will measure it (ruler, tape measure, trundle wheel)
Dependent variable: State how you will measure the time (stopwatch, light gates and computer)
Method: describe what to do
Repeat, remove anomalies and take an average
Calculate the average speed using: average speed = distance travelled (50cm) / average time taken

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9
Q

Describe an experiment to determine the average speed of a trolley rolling down a ramp

A

Set up apparatus as shown in the diagram on OneNote
Independent variable: set the distance between the light gates to 50 cm using a meter ruler
Release the trolley from the start marker
Dependent variable: measure the time it takes for the trolley to travel from one light gate to the next by connecting the light gates to a computer
Repeat several times from the same marker and calculate the average time.
Calculate the average speed using: average speed = distance travelled (50cm) / average time taken

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10
Q

Describe an experiment to determine the average speed of a runner

A

Independent variable: measure a distance of 100 m using a tape measure/ distance; measure using a ruler/tape measure/trundle wheel…; state value(s) to measure (e.g. 100m, or 0 to 100 m in 10 m intervals, )
Dependent variable: time; measure using a stopclock/stopwatch (NOT a timer)
Method: start stopwatch when object starts/passes the initial point. Stop stopwatch when reaches final distance.
Equation: use v=s/t to determine the average speed
OR Analysis: plot a graph of distance against time. Gradient gives the speed

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11
Q

Write down the equation relating acceleration, change in velocity and time taken in words and symbols

A

Acceleration = change in velocity/time taken

a=v-u/t

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12
Q

Plot a velocity-time graph for the following motion: stationary, constant speed, acceleration, deceleration

A

SEE ONENOTE

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13
Q

Describe how acceleration can be determined from a velocity-time graph

A

Calculate the gradient of the line: gradient=Δy/Δx=(Change in velocity)/(Time taken)

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14
Q

Describe how distance/displacement travelled can be determined from a velocity-time graph

A

Calculate the area between the line and the x-axis.
Above the x-axis is a positive displacement. Below the line is a negative displacement. Total displacement is above -below

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15
Q

Write down the equation relating final speed, initial speed, acceleration and distance moved in words and symbols

A

(final speed)^2 = (initial speed)^2 + 2 × acceleration × distance moved
v^2 = u^2 + 2as

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16
Q

Describe the possible effects of forces between bodies

A

Change speed, change direction, change shape

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17
Q

List the different types of fundamental forces

A

Electrostatic, electromagnetic, gravitational, strong, weak

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18
Q

State how a vector quantity is different from a scalar quantity

A

A scalar is a quantity with a magnitude only. A vector is a quantity with a magnitude and direction.

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19
Q

Which of the following are Scalar and which are Vectors?

distance, displacement, speed, velocity, acceleration, time, force, electrical resistance, mass, weight, temperature, pressure, power, momentum, kinetic energy, gravitational potential energy, work done, potential difference (voltage), current

A

Scalar Distance, speed, time, electrical resistance, mass, temperature, pressure, power, kinetic energy, gravitational potential energy, work done, potential difference (voltage), current

Vector Displacement, velocity, acceleration, force, weight, momentum

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20
Q

Describe how to calculate the resultant force of several forces acting along a line

A

Choose one direction as positive and the other direction as negative

Add the quantities together being careful to assign the correct sign depending on the direction

e.g. 9N – 3 N = 6 N. Therefore 6 N to the right

21
Q

Define friction

A

A force that opposes motion

22
Q

Write down the relationship between unbalanced forces, mass and acceleration in words and symbols

A

resultant/net force=mass×acceleration

∑F=ma

23
Q

1.18 Write down the relationship between weight, mass and gravitational field strength in words and symbols

A

weight=mass×gravitational field strength

W=m×g

24
Q

1.19 Define the thinking distance and braking distance

A

Thinking distance: distance travelled from seeing the hazard to pressing the brake

Braking distance: distance travelled from pressing the brake to coming to a complete stop

25
Q

1.19 Define stopping distance

A

The sum of the thinking distance and braking distance

26
Q

1.20 Describe and explain the factors that affect thinking distance

A

Speed – travels further in the same amount of time

Reaction time – affected by alcohol, tiredness, distractions such as using a phone

27
Q

1.20 Describe and explain the factors that affect braking distance

A

Speed – has a greater kinetic energy, therefore longer distance for same force to come to a complete stop. W=Fx. Has a greater momentum, therefore force applied for greater time to come to a complete stop F=Δp/t.

Mass – increases momentum and kinetic energy

Road conditions – reduces braking force

Car conditions – reduces braking force

28
Q

1.21 Describe and sketch the forces acting on a falling object

A

Weight of the object is stronger than the air resistance/fluid friction/drag.

Longer and thicker line from the centre of gravity of the object downwards signifying weight is larger. Smaller and thinner line going upwards is air resistance - smaller.

29
Q

1.21 Define terminal velocity and sketch a diagram

A

Air resistance (or drag) is equal to weight, therefore the object travels at a constant speed.

Arrows upwards and downwards are the same thickness and length

30
Q
  1. 22 Practical: Design an experiment to investigate how extension varies with applied force for
    a. Helical springs
A

Set up apparatus as shown on OneNote

Independent variable: weight applied; add hanging masses to the end of the spring; state values 0 to 1kg in 100g intervals

Dependent variable: extension; measure using a meter ruler to nearest mm

Method: Measure the initial length of the spring. Add masses and record the extension of the spring.

Accuracy: Ruler is vertical and close to mass to avoid parallax error. Repeat the experiment and calculate an average extension.

Analysis: plot a force-extension graph and put a straight line through the appropriate region. It could go past the elastic limit. Gradient gives the spring constant.

31
Q
  1. 22 Practical: Design an experiment to investigate how extension varies with applied force for
    b. Metal wire
A

Similar to a. except use a micrometre to measure the extension of the wire

32
Q
  1. 22 Practical: Design an experiment to investigate how extension varies with applied force for
    c. Rubber band
A

Similar to a. but also measure the extension as masses are removed to show the hysteresis in the graph

33
Q

1.23 Sketch a force-extension graph for a helical spring, metal wire and rubber band and label Hooke’s law region, elastic behaviour, plastic behaviour

A

SEE ONENOTE

34
Q

1.23 State Hooke’s law

A

The extension of the material is proportional to the force applied. The initial linear region of a force-extension graph

35
Q

1.23 Write Hooke’s law as an equation in words and symbols

A

Force=spring constant×extension

F=k×x

36
Q

1.24 Describe elastic behaviour

A

The ability of a material to recover its original shape after the forces causing deformation have been removed

37
Q

1.25P Write down the relationship between momentum, mass and velocity in words and symbols

A

momentum=mass×velocity

p=m×v

38
Q

1.27P State the law of conservation of momentum

A

The total momentum before a collision is equal to the total momentum after a collision

39
Q
  1. 27P Write down the momentum equation for

a. Two objects colliding and separating

A

m_1 u_1+m_2 u_2=m_1 v_1+m_2 v_2

40
Q
  1. 27P Write down the momentum equation for

b. Two objects colliding and sticking

A

m_1 u_1+m_2 u_2=(m_1+m_2)v

41
Q
  1. 27P Write down the momentum equation for

c. Two objects separating due to an explosion

A

0=m_1 v_1+m_2 v_2

42
Q

**1.28P Write down Newton’s 2nd law in terms of momentum

A

The resultant force on an object is equal to the rate of change of momentum

43
Q

1.28P Write down the equation for resultant force in terms of momentum and time taken in words and symbols

A

resultant (net) force=(change in momentum)/Time Taken

∑F=(mv−mu)/t

44
Q

1.26P Describe and explain how safety features work during a collision using the idea of momentum

A

Change in momentum during a collision will remain the same. Increasing the time over which the momentum changes reduces the force on the object (e.g. seat belt, crumple zones on cars, airbags) F=Δp/t

**Increasing the area over which the force is applied will reduce the pressure on the object (e.g. crash helmets, roll bars)

45
Q

1.29P Write down Newton’s 3rd law

A
If object A applies a force on object B, then object B applies a force on object A that is
	• Equal in magnitude
	• Opposite in direction
	• Of the same type of fundamental force
	• Along the same line
46
Q

1.30P Write down the relationship between the moment of a force, force and perpendicular distance from a pivot in words and symbols

A

The turning moment of a force=force×perpendicular distance to pivot
M=F×d

47
Q

1.32P State the principle of moments

A

When an object is in equilibrium, the sum of the clockwise moments is equal to the sum of the anti-clockwise moments

48
Q

1.32P Describe how to use the principle of moments with several parallel forces acting on an object

A

Calculate the clockwise moments
Calculate the anti-clockwise moments

clockwise moments=anti−clockwise moments

Remember also that the vertical and horizontal forces are also balanced, therefore

force to the left=forces to the right
upwards forces=downwards forces

49
Q

1.33P Describe how the upwards force generated by two pivots supporting a beam is affected by the position of a heavy object placed on the beam

A

SEE ONENOTE

The pivot closest to the mass provides the greatest upwards force.
As the woman moves from the left support to the right support, the upwards force on the left pivot will decrease and the upwards force on the right pivot will increase