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Forces Flashcards

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1
Q

What is the formula for average speed?

A

Average speed = distance / time

This can be represented as s = d / t.

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2
Q

What is the formula for acceleration?

A

Acceleration = change in velocity / time taken

This can be represented as a = (v-u) / t.

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3
Q

What defines a vector?

A

Vectors are physical quantities which have both a magnitude and direction

Examples include displacement, velocity, acceleration, force, and weight.

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4
Q

What defines a scalar?

A

Scalars are physical quantities with a magnitude, but not a direction

Examples include distance, speed, time, energy, and mass.

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5
Q

How is average speed typically measured?

A

Average speed is usually measured in m/s

Distance is measured in meters, and time in seconds.

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6
Q

What is the unit of measurement for distance?

A

Distance is measured in meters (m)

Ensure to convert units if necessary, e.g., km.

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7
Q

What is velocity?

A

Velocity is speed in a given direction

It is also measured in m/s.

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8
Q

Give an example where speed is constant but velocity changes.

A

An airplane doing a loop in the sky

The speed remains constant while the direction changes.

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9
Q

What is the relationship between change in velocity and acceleration?

A

Change in velocity is the final velocity minus the initial velocity

Acceleration is measured in m/s².

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10
Q

Fill in the blank: Average speed = _______

A

distance / time

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11
Q

Fill in the blank: Acceleration = _______

A

change in velocity / time taken

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12
Q

What does the gradient represent in a distance-time graph?

A

Velocity

A steeper gradient indicates a higher velocity.

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13
Q

What does a negative gradient in a distance-time graph indicate?

A

Returning back to the starting point

This means the object is moving in the opposite direction.

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14
Q

What does a horizontal line in a distance-time graph represent?

A

Stationary

The object is not moving during this time.

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15
Q

What does a curved line in a distance-time graph indicate?

A

Velocity is changing, and it is accelerating

This indicates that the object is speeding up or slowing down.

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16
Q

In a velocity-time graph, what does the gradient represent?

A

Acceleration

A steeper gradient indicates a higher acceleration.

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17
Q

What does a negative gradient in a velocity-time graph indicate?

A

Deceleration

This means the object is slowing down.

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18
Q

What does a horizontal line in a velocity-time graph represent?

A

Constant speed

The speed remains unchanged over time.

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19
Q

What does the area under the line in a velocity-time graph represent?

A

Distance travelled

This is calculated by multiplying speed and time.

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20
Q

What does a curved line in a velocity-time graph indicate?

A

Changing acceleration

The rate of acceleration is not constant.

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21
Q

In the investigation of toy cars, what was changed to measure speed?

A

The distance the cars were travelling down the ramp

This helps in observing the effect of distance on speed.

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22
Q

How was the speed of the toy cars measured during the experiment?

A

Using a light gate

The light gate triggers when the car passes through, providing a speed measurement.

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23
Q

Fill in the blank: In a distance-time graph, if the distance is zero, it means the object is _______.

A

Back at the starting point

This indicates no movement from the initial position.

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24
Q

What happens when the toy car passes the light gate?

A

The metal square triggers the light gate, and speed is recorded

This provides real-time speed data for the car’s motion.

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25
Q

What is the formula for force?

A

Force (N) = mass (kg) x acceleration (m/s²)

This is often represented as F = m x a.

26
Q

What is the formula for weight?

A

Weight (N) = mass (kg) x gravitational field strength (10 m/s² on Earth)

This is often represented as W = m x g.

27
Q

How is moment calculated?

A

Moment = force x perpendicular distance from the pivot (units are Nm)

Moment is a measure of the tendency of a force to rotate an object about an axis.

28
Q

What type of quantity is force?

A

Force is a vector quantity

This means it has both magnitude and direction.

29
Q

What effects can forces have on a body?

A

Forces can change the speed, shape, or direction of a body

They are measured in Newtons.

30
Q

What are two examples of different types of forces?

A
  • Gravitational
  • Electrostatic

There are many other types of forces as well.

31
Q

What does Newton’s first law state?

A

An object continues in a state of rest or uniform motion until acted on by a resultant force

This implies that an object will maintain its state unless influenced by an external force.

32
Q

What happens to an object if it is moving according to Newton’s first law?

A

It will keep moving at the same speed in a straight line forever until acted on by a resultant force

This means no acceleration or deceleration occurs without a force.

33
Q

What is the resultant force?

A

The overall force acted on an object by two or more forces acting along the same line

It determines the net effect of multiple forces.

34
Q

How do you calculate the resultant force of two or more forces acting along the same line?

A

Add together the forces in the same direction and subtract the forces in the opposite direction

The resultant force acts in the direction of the larger number.

35
Q

What is friction?

A

A force that opposes motion

Air resistance is a form of friction.

36
Q

Fill in the blank: The formula for weight can be expressed as W = m x _______.

A

g

Where g is the gravitational field strength.

37
Q

What is the resultant force when it is zero?

A

Object’s velocity stays the same - including stationary

A zero resultant force means no acceleration or change in motion.

38
Q

What effect does a positive resultant force have on the motion of an object?

A

Object accelerates

A positive resultant force indicates a net force acting in the direction of motion.

39
Q

What effect does a negative resultant force have on the motion of an object?

A

Object decelerates

A negative resultant force indicates a net force acting opposite to the direction of motion.

40
Q

What comprises the total stopping distance of a car?

A

Thinking distance + braking distance

The stopping distance is the total distance required to bring a vehicle to a complete stop.

41
Q

What factors can affect the thinking distance?

A
  • Driver’s fatigue
  • Alcohol consumption
  • Drug influence
  • Distraction
  • Caffeine intake
  • Greater speed

These factors can either increase or decrease the reaction time of the driver.

42
Q

What factors can affect the braking distance?

A
  • Greater speed
  • Mass of vehicle and contents
  • Poor road conditions
  • Condition of the vehicle

These factors influence how quickly a vehicle can come to a halt once brakes are applied.

43
Q

What happens to a falling object initially?

A

Faces no/little air resistance and accelerates downwards due to weight

The force of gravity acts on the object, causing it to fall.

44
Q

What occurs as the downward velocity of a falling object increases?

A

Air resistance increases

This resistance eventually leads to terminal velocity where the object stops accelerating.

45
Q

Fill in the blank: The total distance required to stop a car is equal to the sum of the _______ and the braking distance.

A

thinking distance

46
Q

What is terminal velocity?

A

The point at which air resistance balances the object’s weight.

47
Q

What happens to a skydiver as they fall?

A

They accelerate downwards until they reach terminal velocity.

48
Q

What occurs when a skydiver opens their parachute?

A

Air resistance suddenly increases, resulting in a decrease of speed.

49
Q

What happens to air resistance when the skydiver slows down after opening the parachute?

A

Air resistance decreases until it balances the skydiver’s weight.

50
Q

What is a new lower terminal velocity in the context of skydiving?

A

The reduced terminal velocity that the skydiver reaches after opening the parachute.

51
Q

Fill in the blank: Hooke’s law states that the extension of an object is proportional to the force - up to the _______.

A

elastic limit.

52
Q

Define elastic behaviour.

A

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

53
Q

What happens to elastic objects when the elastic limit is surpassed?

A

They are permanently deformed and the force is no longer proportional to the extension

Elastic objects return to their original shape up to their elastic limit.

54
Q

How can you determine if values are directly proportional?

A

By plotting them on a graph; if the graph is a straight line through the origin, the values are directly proportional

After the elastic limit is reached, the graph becomes a curve.

55
Q

Which materials obey Hooke’s law?

A

Springs and metal wires

Elastic bands do not obey Hooke’s law.

56
Q

What is a moment in physics?

A

A measure of the turning effect of an object

Moments can be clockwise or anticlockwise as they are vector measurements.

57
Q

What does the principle of moments state?

A

When an object is in equilibrium, the total clockwise moment equals the total anticlockwise moment.

58
Q

Where does the weight of a body act?

A

Through its centre of gravity.

59
Q

What condition must be met for a body to be stable?

A

Its centre of gravity must remain vertically above its base.

60
Q

How do columns on a bridge work?

A

They share the weight of the object on the bridge. For example, if a 24,000 N object was in the middle of the bridge with two columns they would share 12,000 N each.

However, if it was 3/4 of the way across, the column it is closer to would experience 3/4 of the weight pushing upwards through it and the other column 1/4.

Physics (12 decks)

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