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GCSE Physics > P8 - Forces in Balance > Flashcards

P8 - Forces in Balance Flashcards

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1
Q

Vector

A

A physical quantity represented by an arrow with direction and magnitude.

(Remember: orange jumpsuit man)

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2
Q

Scalar

A

A physical quantity with only magnitude.

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3
Q

Examples of Vector quantities

A

force, velocity, displacement, acceleration, momentum.

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4
Q

difference between distance and displacement

A

Displacement is distance in a given direction.

  • Displacement is a vector; displacement has a direction and magnitude.
  • Distance is a scalar; distance only has a magnitude.
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5
Q

Force

A

A push or pull,

which acts on an object because of its interaction with another object.

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6
Q

Contact Force

A

A force that only acts on objects when the objects touch each other.

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7
Q

Non-Contact Force

A

A force that acts on objects, but the objects DO NOT touch each other.

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8
Q

Examples of Contact Forces

A
  • Air resistance
  • Tension
  • Thrust
  • Friction
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9
Q

Examples of Non-Contact Forces

A
  • Electrostatic
  • Magnetic
  • Electromagnetic
  • Gravitational
  • Nuclear
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10
Q

Unit of Force

A

The Newton (N).

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11
Q

What can forces do on an object?

A
  • Change the shape
  • Change its motion
  • Change its state of rest.
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12
Q

[True or False] Bikes travelling in different directions have different velocities.

A

True.

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13
Q

Why do bikes have different velocities if they are travelling at the same speed?

A

Because they are travelling in different directions; a vector involves direction and magnitude.

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14
Q

When two forces interact, they ___ exert ___ and ___ forces on ___ ___.

A

When two forces interact, they always exert equal and opposite forces on each other.

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15
Q

Newton’s Third Law

A

When two forces interact, the forces they exert on each other are equal and opposite.

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16
Q

Newton’s First Law of Motion

A

If the resultant force on an object is zero, the object stays at rest if it is stationary, or it keeps moving with the same velocity.

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17
Q

If resultant force on an object is equal to zero:

A

The object stays at rest / the same speed and direction.

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18
Q

If resultant force on an object > zero:

A

The speed or direction of the object will change.

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19
Q

If two forces act on an object along the same line in the same direction, the resultant force is …

A

… their sum.

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20
Q

If two forces act on an object along the same line in opposite directions, the resultant force is …

A

… their difference.

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21
Q

What does a free-body force diagram of an object show?

A

The forces acting on it.

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22
Q

What can resultant forces be?

A

Balanced or unbalanced.

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23
Q

[True or False] When the resultant force on an object is zero, it is stationary.

A

False.

It may also be travelling at the same velocity / the same constant speed in the same direction.

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24
Q

[True or False] Forces on a diagram should always be clearly labelled.

A

True.

Force diagrams usually show more than one force.

25
Q

[Newton’s Third Law] If the forces are always equal, how does anything ever go anywhere?

A

The two forces are acting on different objects; the effects of these forces on each object depends on the masses of the objects.

Larger mass, smaller effect.

26
Q

What is the driving force on a car?

A

The force that makes the car move.

This is sometimes called the engine force or the motive force.

27
Q

How does the driving force push the car forward?

A

Because there is friction between the ground and the tyre.

28
Q

[Friction in action] When the car moves forward:

A
  • Force of the friction on the ROAD on the TYRE is in the forward direction.
  • Force of friction of TYRE on the ROAD is in the reverse direction.

See kerboodle: pg101 Figure 3 - Driving Force diagram. (AQA Combined Science Physics)

29
Q

When a force moves an object through a ___, ___ ___ ___ and ___ ___ ___ on the object.

A

When a force moves an object through a distance, ENERGY IS TRANSFERRED and WORK IS DONE on the object.

30
Q

Centre of mass

A

The point where the mass of an object can be thought of as being concentrated.

31
Q

Method to finding the centre of mass of an irregular polygon / irregularly-shaped object

A
  1. Hang your card from a clamp stand, along with a plumb bob.
  2. Draw a line along the plumb bob’s string.
  3. Repeat two or more times.
  4. The centre of mass will be located at the intersection of the lines.
32
Q

When an object is freely suspended …

A

it comes to rest with its centre of mass directly underneath the point of suspension.

33
Q

[True or False] The centre of mass of a symmetrical object is along the axis of symmetry.

A

True.

34
Q

Stable Equilibrium

A

An object is said to be in stable equilibrium:

  • If it returns to its original position when it is disturbed.
35
Q

Unstable Equilibrium

A

An object is said to be in unstable equilibrium:

  • If it falls or topples when it is disturbed.
36
Q

Neutral Equilibrium

A

An object is said to be in neutral equilibrium:

  • If it remains in its new position when disturbed.
37
Q

Example of Stable Equilibrium

A

A book resting on the ground.

38
Q

Example of Unstable Equilibrium

A

Apex of an ice cream cone balancing on top of a book.

The movement of the book will disturb the position of the ice cream cone.

39
Q

Example of Neutral Equilibrium

A

A marble or rolling ball on a flat horizontal surface.

40
Q

Factors affecting Stability

A
  • Base width

- Height of centre of mass

41
Q

Centre of Gravity, Centre of Mass

A

Essentially the same thing for the time being.

42
Q

Gravitational Force

A

The force of attraction between masses

43
Q

Formula for weight of an object IF you know its mass (m) and strength of the gravitational field (N/kg)

A

Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)

For Earth, it is 9.8 N/kg

For the Moon, it is around 1.6 N/kg

44
Q

Mass is ___ ___ to Weight

A

Directly Proportional

45
Q

Resultant force

A

The overall force on a point or object.

46
Q

If a ___ Force ___ an object, ___ ___ ___

A

If a RESULTANT Force MOVES an object, WORK IS DONE.

47
Q

The parallelogram of forces is a ___ ___ of two force ___

A

The parallelogram of forces is a SCALE DIAGRAM of two force VECTORS.

48
Q

Use of the parallelogram of forces

A

Used to find the resultant of two forces that do NOT act along the same line.

49
Q

What is the resultant force vector of a parallelogram of forces?

A

The resultant is the diagonal of the parallelogram that starts at the origin of the two forces.

50
Q

Normal Contact Force

A

The equal and opposite force that surfaces exert to prevent solid objects from passing through each other.

The normal contact force is always perpendicular to the gradient / slope an object is on

Normal = 90 degrees; perpendicular ...
Contact = Touching
51
Q

What does it mean to resolve a force?

A

Finding components perpendicular to each other that have a resultant force that is equal to the force in question.

This is informally known as “Splitting a vector into its components”.

52
Q

How to resolve a force in two perpendicular directions

A

Draw a rectangle with adjacent sides ALONG the perpendicular components; along the two directions.

This is so that the diagonal shows the force vector.

53
Q

What is the resultant force for an object in equilibrium?

A

Zero.

54
Q

Why would an object at rest be in equilibrium?

A

Because the resultant force acting on it is zero.

55
Q

‘Adding’ Vectors

A

Finding the resultant force when given any amount of vectors.

Informally: “Adding any number of vectors acting in the same direction”.

56
Q

An object is in ___ if the ___ on it are ___

A

An Object is in EQUILIBRIUM if the FORCES on it are BALANCED.

57
Q

What is the Parallelogram of forces?

A

A geometrical method to find the resultant of two forces that don’t act along the same line.

58
Q

Friction

A

The force opposing the relative motion of two solid surfaces in contact.

GCSE Physics (3 decks)

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