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physics > Forces and Motion > Flashcards

Forces and Motion Flashcards

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1
Q

What is distance

A

Distance is the length of the path traveled during a journey

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2
Q

What is displacement

A

Displacement is the distance covered in a particular direction

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3
Q

What is the equation for average speed

A

Average speed = distance / time

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4
Q

What is the equation for average velocity

A

Average velocity = displacement / time

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5
Q

What is acceleration

A

Acceleration is the rate of change in velocity

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6
Q

What is the equation for acceleration

A

Acceleration = change in velocity / time taken
= final velocity - initial velocity / t

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7
Q

What is the gradient of a distance-time graph equal to

A

Speed

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8
Q

What does a horizontal line on a distance-time graph tell us

A

The object is stationary

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9
Q

What does a curve on a distance-time graph tell us

A

The object is accelerating

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10
Q

What is the gradient of a velocity-time graph equal to

A

The acceleration

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11
Q

What is the area of a velocity-time graph equal to

A

The distance traveled

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12
Q

What does a horizontal line on a velocity-time graph tell us

A

Constant speed

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13
Q

What does a downward line on a velocity-time graph tell us

A

Constant deceleration

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14
Q

What is the equation to find the displacement of an object moving with a constant acceleration

A

final velocity squared = initial velocity squared + 2 * acceleration * displacement

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15
Q

Is force a vector or a scalar

A

Force is a vector

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16
Q

What are the two types of forces

A

Contact forces and non contact forces

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17
Q

Name the different types of contact forces

A

Normal reaction force
Tension
Friction
Air-resistance
Upthrust
Thrust
Lift

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18
Q

What is the normal reaction force

A

The normal reaction force is the repulsive force that prevents two touching bodies from moving into each other. It acts at 90 degrees to the surface of the bodies

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19
Q

What is tension

A

Tension is the force that an object being stretched experiences. It acts along the direction of stretching

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20
Q

What is friction

A

Friction is the force that opposes motion between surfaces that slide past each other. The kinetic energy of the moving object is converted to heat by the force of friction

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21
Q

What is air resistance

A

Air resistance is the force that opposes the movement of objects through air. It increases with an increase in speed and surface area

22
Q

What is upthrust

A

Upthrust is the upward force experienced by an object partially or fully submerged in a fluid. This is because greater pressure acts on its bottom surface than on its top surface which causes an upward resultant force

23
Q

What is thrust

A

Thrust is the force that drives vehicles forward as a result of the expulsion of fluid in the opposite direction

24
Q

Name the non-contact forces

A

Gravitational force / Weight
Magnetic force
Electrostatic force

25
Q

What is weight

A

Weight is the gravitational pull of the Earth on an object towards the center of the Earth

26
Q

What is mass

A

Mass is the amount of substance of an object

27
Q

What is the equation for weight

A

Weight = mass * gravitational field strength

28
Q

What is the resultant force

A

The resultant force is the single force that replaces all forces acting on a body

29
Q

How do we calculate the resulatant force

A

Add together all the forces acting along the same direction and subtract the forces acting in opposite directions

30
Q

What does Newton’s first law of motion state

A

An object will remain at rest or continue moving at a constant speed as long as the forces acting on it are balanced

31
Q

What is Newton’s second law of motion

A

The acceleration of an object is directly proportional to the resultant force and inversely proportional to its mass

32
Q

How is the acceleration of a body dependent upon the direction of motion

A

If the resultant force is in the same direction as the motion, the body will accelerate. If the resultant force is in the opposite direction to the motion, the body will decelerate

33
Q

Write newton’s second law mathematically

A

Resultant force = Mass * acceleration

34
Q

Explain how forces acting on a skydiver change his velocity as he falls from the helicopter to the ground

A

When the skydiver falls from the helicopter, his velocity is 0 m/s and the only force acting on him is his weight, causing him to accelerate very quickly downwards. However, as he accelerates and his speed increases, so does air resistance which acts in the opposite direction of motion, resulting in his acceleration to decrease. Eventually, the air resistance will balance out the force of the weight, resulting in the resultant force being 0 and consequently, according to Newton’s 1st law, the object will keep falling with a constant speed knows as terminal velocity. When the parachute is opened, the air resistance becomes much bigger due to the increase in surface area. Since it is greater than the weight and acting in the opposite direction of motion, the object will start to decelerate. However as its speed is decreasing so will the air resistance acting on the object, resulting in the deceleration becoming smaller and smaller. Eventually it will balance out the weight of the object and the parcel will consequently fall with a lower, constant speed

35
Q

What is Newton’s third law

A

Every action has an equal and opposite reaction

36
Q

What are the 5 conditions needed for two forces to form a newton third pair

A

Same size
Same type
Act in the same line of action
Act on two different objects
Act in the opposite direction

37
Q

What is the thinking distance

A

The thinking distance is the distance covered during the reaction time of the driver

38
Q

What is the braking distance

A

The braking distance is the distance covered after the driver has applied the brakes

39
Q

What is the stopping distance

A

The stopping distance is the sum of the thinking distance and the braking distance

40
Q

List the 5 factors that increase the thinking distance

A

Poor visibility
Driver is tired
Driver is distracted
Driver is influenced by alcohol
Speed (proportional to thinking distance)

41
Q

List the 4 factors that increase the braking distance

A

Higher speed
Worn brakes
Mass of car
Road conditions

42
Q

What happens to the thinking distance when the speed of the car is doubled

A

It is doubled

43
Q

What happens to the braking distance when the speed of the car is doubled

A

It is quadrupled

44
Q

What is elastic deformation

A

Elastic deformation occurs when a material returns to its original shape after the deforming force is removed

45
Q

What is plastic deformation

A

Plastic deformation occurs when a material remains deformed after the force is removed

46
Q

What does Hooke’s Law state

A

Hooke’s Law states that the extension of a material is directly proportional to the applied force, up to the limit of proportionality

47
Q

What is the formula for Hooke’s Law

A

Force = k (stiffness) * extension

48
Q

What does stiffness depend on

A

Material the spring is made form
Dimensions (length, thickness)

49
Q

What is the limit of proportionality

A

The point above which the spring stops obey Hooke’s law as the force is no longer directly proportional to the extension

50
Q

What is the elastic limit

A

The point above which the spring stops showing elastic behavior and it changes shape permanently

physics (7 decks)

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