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Physics > Topic 5 - Forces > Flashcards

Topic 5 - Forces Flashcards

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1
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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2
Q

What unit is force measured in ?

A

Newtons (N)

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3
Q

Are forces classed as a vector or scalar quantities and why?

A

-vector
- because they have both magnitude and direction

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4
Q

what is a contact force?

A

the objects are physically touching

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5
Q

what is a non- contact force?

A

the objects are physically separated.

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6
Q

Name 4 types of contact forces

A

-friction,
-air resistance,
-tension
-normal contact force

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7
Q

Name 3 non contact forces

A

gravitational force,
electrostatic force
magnetic force

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8
Q

Is air resistance a contact or non-contact force? Explain why.

A

Air resistance is a contact force. This is because it is due to the physical contact (collisions) between an object and the particles in the air.

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9
Q

what are scalars?

A

quantities with a magnitude (size) only.

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10
Q

what are vectors?

A

describes a movement from one point to another. A vector quantity has both direction. and magnitude. (size).

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11
Q

name 4 examples of scalar quantities

A

-time
-temperature
-speed
-distance

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12
Q

Name 4 examples of vector quantities

A

-velocity
-displacement
- acceleration
-momentum
-force

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13
Q

What is meant by the term equilibrium?

A

when the forces acting on an object are all balanced, so the resultant force is 0

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14
Q

What is an elastic object?

A

one that regains its shape when the forces demorming it are removed

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15
Q

Fill in the gaps:

When an elastic object is ______________ the energy which caused it to deform is stored as ______ __________ which is released when the force is _________

A

-deformed
- elastic energy
- removed

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16
Q

What is hookes law?

A

the extension of a spring is directly proportional to the force applied, provided its limit of proportionality is not exceeded
F=Ke

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17
Q

What is the method for the hookes law practical (6 steps)?

A
  1. hang the spring to the clamp and add a splint so its easier to read the length
  2. check that the splint is horizontal. take a reading on the ruler(lenght of unstretched spring at weight 0.0N)
  3. hook the 100g mass hanger on the bottom of the spring. (1N)
  4. take a reading of the length of the spring
  5. add further masses(100g each time) and measure and record the length of the spring for at least 8 times
  6. calculate the extension.by subtracting unstretched spring lenght from each length recording
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18
Q

What is an objects spring constant?

A

a measure of how many Newtons of force it would require to stretch (or compress) the object by 1 metre. It has the units
N/m.

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19
Q

Fill in the blank:
Objects with a _____________ spring constant are more stiff, so they require_____force to stretch.

A

Objects with a higher spring constant are more stiff, so they requiremoreforce to stretch.

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20
Q

what does each symbol represent in this equation (hookes law)?
𝐹=𝑘e

A

Fis the force applied to the spring,𝑘is the spring constant, and𝑒is the extension.

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21
Q

If you stretch an object too much it can pass its ‘elastic limit’ (also known as the ‘limit of proportionality’).
At this point what will happen to the object?

A

It will start deforming inelastically

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22
Q

Fill in the blank:
objects with a __________ spring constant are more elastic so they require _____ force to stretch

A

lower
less

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23
Q

What is the equation to work out the elastic potential energy of an object?

A

𝐸𝑒=1/2𝑘𝑒²

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24
Q

what do the symbols in this equation represent?
𝐸𝑒=1/2𝑘𝑒²

A

𝐸𝑒 (elastic potential energy J)
𝑘 (spring constant N/m)
𝑒² (extention m)

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25
Q

In a graph representing hookes law, The gradient of the straight part of the graph tells us the:

A

spring constant

26
Q

In a graph representing hookes law, The area under the curve tells us the:

A

Elastic potential energy

27
Q

In a graph representing hookes law, The point where the line goes from straight to curved is referred to as the:

A

Limit of proportionality
or
Elastic limit

28
Q

What is a moment?

A

the turning effect of a force around a fixed pivot

29
Q

What is the formula for moment?

A

Moment (NM)= force(F) x Distance from pivot (m)

30
Q

What would happen to an object if the forces are balanced and the resultant force is 0?

A

the object will stay in the same state of motion

31
Q

What is the resultant force of an object?

A

the single overall force acting on an object

32
Q

What two things does the size of a moment depend on?

A

-size of force
- perpendicular distance between force and pivot

33
Q

What is the equation that links weight mass and gravity?

A

Weight (w) = Mass (m) x gravity (g)

34
Q

What is the equation that links pressure force and area?

A

Pressure (Pa) = force (N) / area (m²)

35
Q

How can you increase the pressure on a given point in a fluid?

A

increase the height of the fluid above the point

36
Q

The pressure in a liquid depends on: (2 things)

A

-density of liquid
- depth

37
Q

What is the unit for pressure?

A

pascals (Pa)

38
Q

What is the formula for pressure in a liquid?

A

Pressure (n/m²) = density x gravity x height

39
Q

True or false:
air pressure is equal in all directions

A

true

40
Q

What is air pressure caused by?

A

the force of air gas particles bumping into things

41
Q

What is upthrust?

A

the upward force that a fluid exerts on a body floating in it

42
Q

An object floats when its weight is _______ to the _____________ provided by the liquid

A

equal
upthrust

43
Q

An object sinks when its weight is __________ than the __________ provided by the fluid

A

greater
upthrust

44
Q

Pressure in a gas is caused by particles ____________. the more frequent collisions and the greater their force, the ___________ the pressure

A

colliding
greater

45
Q

IS distance a scalar or vector quantity and why?

A

-scalar
- it only has a magnitude and is a measure of how far an object has travelled

46
Q

IS displacement a scalar or vector quantity and why?

A
  • vector
  • has magnitude and direction
47
Q

What is the equation that links speed distance and time?

A

speed (m/s) = distance/ time

48
Q

What is the equation that links velocity displacement and time?

A

velocity (m/s) = displacement/ time

49
Q

what is acceleration?

A

the rate of change in velocity

50
Q

What is acceleration measured in ?

A

m/s²

51
Q

What is the equation for acceleration if given the time?

A

acceleration = change in velocity / time taken

52
Q

What is the equation for acceleration if distance is given?

A

acceleration = final velocity² - initial velocity²

53
Q

As the velocity of a falling object increases, the air resistance:

A

increases

54
Q

Terminal velocity is reached when:

A

The resultant force is zero
and
The weight has the same magnitude as the air resistance

55
Q

What does newtons 1st law state?

A

if forces acting on an object are balanced then if it is still it will stay still and if it is moving it will keep moving at a constant speed in a straight line

56
Q

what does newtons 2nd law state?

A

A resultant force will cause an object to accelerate in the direction of the force. the acceleration is directly proportional to the force and inversley proportional to the mass Force = mass x acceleration

57
Q

What does newtons 3rd law state?

A

for every action there is an equal and opposite reaction however the force mut be of the same type

58
Q

What is momentum?

A

the tendency of an object to keep moving in the same direction

59
Q

Is momentum scalar or vector?

A

vector

60
Q

What is the equation that links momentum (kg m/s) mass and velocity?

A

momentum= mass x velocity

61
Q

What does the conservation of momentum state?

A

in a ‘closed system’ the total momentum before an event is equal to the total momentum after the event

Physics (5 decks)

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