Forces Flashcards

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1
Q

What is a scalar quantity?

A

One that has magnitude (size) but not direction

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2
Q

What is a vector quantity?

A

One that has magnitude (size) and direction

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3
Q

What are some examples of a scalar quantity?

A

Distance
Energy
Speed

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4
Q

What are some examples of a vector quantity?

A

Displacement
Velocity
Acceleration

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5
Q

What is normal contact force?

A

The support force exerted upon an object that is in contact with another stable object; the normal contact force is always perpendicular to the surface

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6
Q

What are some examples of non-contact forces?

A

Electrostatic, magnetic and gravitational

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7
Q

What is the centre of mass?

A

The point in an object from which its weight acts
If the forces on an object are balanced, we say that the object is in equilibrium

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8
Q

What is the equation for finding work done using displacement?

A

W = F x s

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9
Q

Who discovered a law for elastic materials?

A

Robert Hooke

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10
Q

What does Hooke’s law state?

A

The extension of an elastic object is directly proportional to the force applied, provided the limit of proportionality is not exceeded

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11
Q

What is the equation created by Hooke’s law?

A

Force = spring constant x extension

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12
Q

What do levers do?

A

They are used to produce a turning effect with ease in order to make tasks easier e.g. opening a door

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13
Q

What is a moment?

A

A measure of a forces tendency to cause a body to rotate

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14
Q

What can cause a moment to increase?

A

The size of the applied force
The perpendicular distance from a pivot the force is applied

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15
Q

What is the equation to calculate a moment?

A

Moment = force x distance

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16
Q

What are pulleys and gears used for?

A

Increasing or decreasing a rotational force (turning effect) in machines

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17
Q

What is the equation to calculate a moment when a gear is involved?

A

Moment = force x gear radius

18
Q

What is an output?

A

A low speed and provides a high turning effect / moment - low gear

19
Q

What is an input?

A

Input is a high speed and a low turning effect - high gear

20
Q

How do you calculate pressure?

A

P1 = P2
F1/A1 = F2/A2

21
Q

How do you calculate liquid pressure?

A

Pressure = height of column of liquid x density x gravitational field

22
Q

What is the upthrust?

A

The force that is equal in size but opposite in direction to the weight of the fluid that is displaced by the object

23
Q

How can we increase pressure?

A

Making the container smaller
Heating up the particles

24
Q

Why do objects float?

A

If the object is less dense than the liquid it’s in it will float

25
Q

Why is velocity a vector quantity?

A

Because it is speed in a direction

26
Q

What is constant acceleration also called and what does it mean?

A

Uniform acceleration meaning that the value of acceleration stays the same during acceleration or deceleration

27
Q

What is Newton’s first law of motion?

A

If the net force acting on an object is zero, then the object will remain at rest or at constant velocity

28
Q

What is Newton’s second law of motion?

A

If a force acts upon an object with mass then it will experience an acceleration

29
Q

What is Newton’s third law of motion?

A

If an object exerts a force on another object, then the second object will exert an equal and opposite force on the first object

30
Q

What is friction called in a fluid?

A

Drag

31
Q

What does the magnitude of resistance depend on?

A

Speed
The size of the cross sectional area

32
Q

What happens if the speed or size of the cross sectional area increases?

A

The air resistance increases

33
Q

Describe all of the forces that occur to a skydiver and what they mean

A

1) When a skydiver jumps out of a plane, the downward force of their weight pulls them down and they will accelerate
2) As they accelerate, the air resistance force increases and acts in the opposite direction to the skydiver’s weight
3) Eventually, the force of the air resistance will equal the force of the weight and the skydiver will now be at a constant speed and has reached terminal velocity
4) When the parachute is opened, there is now a very large air resistance force and they will begin to decelerate
5) As they decelerate, the air resistance force on the parachute decreases until it is the same size as their weight and they are again falling at terminal velocity but at a slower speed
6) On the ground their weight is now equal to the upwards force from the ground and the forces are balanced

34
Q

What affects the stopping distance of a vehicle?

A

The thinking distance and the braking distance

35
Q

What can affect thinking distance?

A

Tiredness
Drugs or alcohol
Mobile phone
Driving too fast

36
Q

What can affect braking distance?

A

Icy roads
Tyres / brakes worn out
Wet roads
Driving too fast

37
Q

What does the law of conservation of momentum state?

A

The total momentum before an event is the same as the total momentum, after the event, provided no external forces act on the system

38
Q

How does impact time affect impact force and why?

A

The longer the impact time, the smaller the impact force because the force is inversely proportional to the acceleration and the force is also inversely proportional to the time

39
Q

What is the crumple zone of a vehicle?

A

An area designed to crush in a controlled way during a collision to increase impact time and decrease impact force

40
Q

What is the definition of acceleration?

A

The change in velocity every second