P2: Forces Flashcards

1
Q

What are scalars?

A

Quantities with only magnitude.

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2
Q

What are vectors?

A

Quantities with magnitude AND direction.

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3
Q

Give some examples of contact forces.

A

Friction, air resistance, tension.

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4
Q

Give examples of non-contact forces.

A

Electrostatic, magnetic, gravitational.

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5
Q

If an object has zero resultant force, what is it doing?

A

Either travelling at a constant speed or not moving.

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6
Q

What is a resultant force?

A

The overall effect of several forces added together.

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7
Q

What is it called when all of the forces acting on an object are balanced?

A

Equilibrium.

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8
Q

Where is the centre of mass on an object?

A

Where all of the lines of symmetry cross.

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9
Q

What is the difference between mass and weight?

A

Mass is the quantity of matter in an object, weight is a force acting on an object. Weight depends on the strength of the gravitational field, mass does not.

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10
Q

What is the moment of a force?

A

The turning effect of the force.

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11
Q

How do you calculate the moment of a force?

A

Moment = Force x Distance

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12
Q

What does a lever do?

A

Increases the turning effect without you needing to use more force.

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13
Q

What are gears used for?

A

Transmitting the rotational effects of forces. Apply the same force, but with different moments.

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14
Q

Describe the gear movement for a bike on a low gear.

A

The small gear turns the large gear. Same speed but lower moment.

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15
Q

Describe the gear movement for a bike on a high gear.

A

Large gear turning the small gear. Same speed but a higher moment.

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16
Q

What states of matter are fluids?

A

Liquids and gases.

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17
Q

Describe the movement of particles in fluids.

A

Can move around freely.

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18
Q

Describe the movement of particles in solids.

A

Can only vibrate around a fixed position.

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19
Q

What happens when an object is placed in a fluid?

A

The fluid’s particles constantly collide with it.

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20
Q

Describe how the density of the atmosphere changes at different altitudes.

A

The higher the altitude, the less dense the atmosphere, so the lower the atmospheric pressure (because the number of air molecules decreases).

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21
Q

Describe how pressure changes as depth changes in a fluid.

A

Pressure increases with depth because of the weight of the liquid above.

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22
Q

List the three things that pressure in a liquid is affected by.

A

Height, density, gravitational field strength.

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23
Q

What is the equation for pressure in a liquid?

A

Pressure = height x density x gravitational field strength

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24
Q

What is displacement?

A

How far an object moves measured from start to finish in a straight line. The overall change in the position of an object

25
Q

What is the difference between velocity and speed?

A

Velocity is a vector quantity (has direction), speed is a scalar quantity

26
Q

What does uniform acceleration mean?

A

The amount of acceleration doesn’t change.

27
Q

What is Newton’s first law?

A

States the movement of an object with 0 resultant force will remain constant.

28
Q

What is Newton’s Second Law?

A

States that resultant force = mass x acceleration

29
Q

What is Newton’s Third Law?

A

When two objects interact, they exert an equal and opposite force on eachother.

30
Q

What is inertia?

A

The tendency of objects with mass to stay at rest or in the same state of motion.

31
Q

How do you calculate inertial mass?

A

mass = force/area

32
Q

What is the equation for stopping distance of a vehicle?

A

Stopping distance of a vehicle = thinking distance + braking distance.

33
Q

What factors affect thinking distance?

A

Tiredness, use of drugs.

34
Q

What is thinking distance?

A

How far the vehicle travels during the driver’s reaction time.

35
Q

What is braking distance?

A

The distance travelled once the brakes have been applied.

36
Q

What is braking distance affected by?

A

Poor condition of the vehicle, weather conditions, wet or icy roads and poor road surfaces.

37
Q

State the equation that links braking distance and velocity.

A

Braking distance = k x velocity^2

38
Q

What do brakes use to slow down wheels?

A

Friction.

39
Q

Describe how brakes work.

A

The work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle.

40
Q

What are the two things that acceleration depends on?

A

Force and mass.

41
Q

What equipment do you need to test how changing the force applied to a trolley changes its acceleration?

A

Trolley, pulley, slotted masses, two light gates, track

42
Q

How do you reduce the effect of friction when calculating acceleration in an RPA?

A

Use an air track, or make a slope

43
Q

Explain why the temperature of brakes increases as they are used.

A

-Work is done due to friction
-Causing an increase in the thermal energy of the breaks

44
Q

What is a closed system?

A

A system where the total energy remains constant.

45
Q

How could a driver of a car increase the moment about the pivot of the handbrake lever

A

Make the driver place their hand at the end of the lever

46
Q

The driver of a car is distracted, and needs to apply the breaks suddenly to stop the car. Explain why the distraction will increase the stopping distance.

A

-Stopping distance includes thinking distance
-There is an additional time before the driver applies the brakes
-So the thinking distance will increase

47
Q

How does having a flexible layer of protection reduce the damage done on collision?

A

-Increases time taken for the collision to occur
-So the rate of change of momentum decreases
-So the force is reduced

48
Q

What type of deformation is it if the deformation is reversed when the force is removed?

A

Elastic.

49
Q

What is the opposite of elastic deformation?

A

Inelastic deformation.

50
Q

What type of deformation is it, if it is not fully reversed when the force is removed?

A

Inelastic deformation.

51
Q

What is the elastic limit?

A

The furthest point a material can be stretched or deformed while being able to return to its previous shape.

52
Q

The higher the spring constant, the ___ the string?

A

Stiffer.

53
Q

What is the equation of Hooke’s law?

A

Force = Spring constant x extension

54
Q

When testing how forces affect the extension of a spring, what should be done to avoid equipment falling off the table?

A

Use a G-clamp to secure the stand.

55
Q

When testing how forces affect the extension of a spring, what should be done to avoid the sharp end of the spring recoiling if the spring breaks?

A

Support and gently lower masses whilst loading the spring, and wear eye protection.

56
Q

When testing how forces affect the extension of a spring, what should be done to avoid masses falling to the floor if the spring fails?

A

Gently lowering the load onto the spring and taking a step back.

57
Q

What is momentum?

A

The product of mass and velocity.

58
Q

What is Hooke’s law?

A

The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.