P8 - Forces In Balance Flashcards

(52 cards)

1
Q

What is the difference between scalar and vector quantities?

A

Scalar quantities have magnitude only, vector quantities have magnitude and direction

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2
Q

How can a vector quantity be represented?

A

An arrow

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3
Q

What is a force?

A

A push or pull that acts on an object due to the interaction with another object

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4
Q

What are contact forces and give 4 examples?

A
  • Objects are physically touching
  • Friction, air resistance, tension, normal
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5
Q

What are non contact forces, give 3 examples?

A
  • Objects are physically separated
  • Gravitational, electrostatic, magnetic
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6
Q

What is weight?

A

A force acting on an object due to gravity

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7
Q

What type of quantity is force?

A

Vector

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8
Q

What causes the force of gravity close to Earth?

A

Gravitational field around the Earth

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9
Q

What does the weight of an object depend on?

A

The gravitation field strength at the point where the object is at

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10
Q

What is the equation that links gravitational field strength, mass and weight?

A

weight(N)=mass(kg)* gravitational field strength (N/kg)

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11
Q

What happens when the resultant force is 0?

A
  • Forces are balanced meaning movement will not change(direction can’t change)
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12
Q

What is the centre of mass?

A

Point at which weight of an object acts through

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13
Q

What is the relationship between the weight and mass of an object?

A

The weight of an object and the mass of an object are directly proportional

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14
Q

What is the resultant force?

A

A single force that is the result of all different forces acting on the object

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15
Q

What happens when there is a resultant force?

A

Speed or shape or direction changes

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16
Q

Describe examples of the forces acting on an isolated object or system

A
  • Gravitational force(like in planets)
  • Electromagnetic force(as in magnets)
  • Nuclear force(within atomic nucleus)
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17
Q

What is an isolated object?

A
  • A system which isn’t influened by other external systems but experiences internal forces
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18
Q

What are free body diagrams used for?

A

Used to describe situations where several forces act on the object

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19
Q

What can a single force be resolved into?

A
  • Two components acting at right angles to each other
  • Have the same effect as the single force
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20
Q

When is work done on an object?

A

When a force causes displacement of an object

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21
Q

What is the equation that links distance, force and work done?

A

work done(J) = force(N)* distance(m)

22
Q

How many NM(newton metres) is 1 Joule?

A

1 newton-metre

23
Q

What causes a rise in the temperature of an object?

A

Work done against the frictional forces acting on an object

24
Q

Illustrate resolution of forces, equilibrium situations and determine the resultant of two forces to include both magnitude and direction

A
  • Skydiver’s weight acts on him pulling him towards the ground
  • Drag (air resistsance) acts on him too, opposite to his motion
  • Sizes of arrows show magnitudes of forces and directions show direction of forces
25
Give examples of the forces involved in stretching, bending or compressing an object
1. The spring is compressed when opposing forces act toward the object, the spring is stretched when opposing forces act away from the object. 2. Forces on a diving board cause it to bend when a swimmer stands on one end. 3. Multiple forces act in opposing directions at different points on the object causing it to bend.
26
Why must more than one force be applied to change the shape of a stationary object by stretching, bending or compressing?
Because a single force would simply cause the object to move in the direciton in which the force were to be applied
27
What is the difference between elastic and inelastic deformation?
- Elastic deformation is reversible and temporary when load is removed - Inelastic deformation is permanent and irreversible even when the load is removed
28
Give an example of an elastic object
Spring
29
What is the relationship between the extension or compression of an elastic object and the force applied?(2)
- Extension is directly proportional to the force applied to it - Provided that the limit of proportionality is not exceeded
30
What is the equation that links extension, force and spring constant?
force = spring constant * extension
31
What is the unit for spring constant?
N/m
32
What is the unit for extension?
m
33
Describe the energy transfer involved when a force stretches or compresses a spring
- Force does work on the spring - Energy is transferred mechanically to the elastic potential energy store of the object - Provided that the spring is not inelastically deformed - The work done on the spring is equal to the elastic potential energy
34
What is the difference between a linear and non-linear relationship between force and extension?
- Linear: Gradient of the force-extension graph is equal to the spring constant as the relationship between force and extension is directly proportional - Non-linear: Gradient of the force-extension graph is not equal to the spring constant as force and extension are not directly proportional, the extension increases more for each unit increase in force
35
What is the equation to calcualte the work done in stretching/compressing a spring?
EPE = 1/2 * spring constant * (extension)^2
36
What is Newton's first law?
If the resultant force is zero: - stationary object status stationary - moving objects keep moving at same velocity(speed + direction)
37
What is inertia?
Tendency of objects to stay at same speed or stationary
38
What is Newton's second law?
- Objects accelerate if a resultant force is acting on them - Acceleration is proportional to magnitude - Accelartion is inversely proportional to mass - F=ma
39
What is Newton's third law?
- When two objects interact, they exert equal and opposite forces on each other - Each act on separate objects, are the same size, act in opposite directions, same type
40
What form of energy is stored in a stretched spring?
Elastic
41
Examples in which forces cause rotation?
- Door opening around a hinge - Seesaw rotating around its pivot - Spanner turning a nut
42
What is the turning effect of a force otherwise known as?
Moment of a force
43
What is the equation that links distance, force and moment of a force?
moment = force * distance
44
What is the unit for the moment of a force?
Newton meter(Nm)
45
What is the distance in the moment equation?
- Perpendicular distance from pivot to the line of action of the force in metres
46
What happens in an object is balanced?
- Total clockwise moment about pviot = total anticlockwise moment about pivot
47
What can a simple lever and a simple gear system be used to do?
Transmit the rotational effect of forces
48
Explain how levers transmit the rotational effects of forces
- As one end of a pivot has effort applied to it - The opposite end of the pivot also rotates in the same direction
49
Explain how gears transmit the rotational effects of forces
- As one gear rotates, its teeth interlock with the other gear making it rotate X times as much
50
How can you determine the centre of mass
1. Three holes in card, different places close to the edge 2. Place a pin through first hole and hold pin in place using boss in clamp stand to suspend the card 3. Tie weight to string and suspend from pin --> plumb line 4. Draw line marking where the string was, repeat for other two - point where they intersect is the centre of mass
51
How can you check the centre of mass is accurate?
- Put another hole near edge - Suspend using pin and create plumb line - Draw line, intersects centre of mass it is accurate
52
Explain when an object will topple over
- Centre of mass at point at which weight of object acts through object topple over when centre falls outside the base of objects