Topic 2: Mechanics Flashcards

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1
Q

Define scalars.

A

Quantities with only a magnitude (size) eg. temperature, distance.

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2
Q

Define vectors.

A

Quantities with both magnitude and direction eg. displacement.

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3
Q

Define distance (d).

A

How far you have travelled. Measured in metres (m).

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4
Q

Define displacement (s).

A

The distance travelled in a particular direction. Measured in metres (m).

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5
Q

Define speed.

A

The rate of change of distance (distance divided by time). Measured in ms⁻¹.

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6
Q

Define velocity.

A

The rate of change of displacement (displacement divided by time). Measured in ms⁻¹.

Initial velocity = u
Final velocity = v

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7
Q

Define instantaneous speed.

A

The rate of change of distance at one particular time.

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8
Q

Define average speed.

A

The speed over a period of time (the total distance divided by the total time).

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9
Q

Define acceleration (a).

A

The rate of change of velocity (change in velocity divided by time). Measured in ms⁻².

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10
Q

When do the equations of motion given in the data booklet apply?

A

When the object is accelerating at a constant rate (uniform acceleration).

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11
Q

What is the gradient of displacement-time graphs?

A

In displacement-time graphs the gradient is the velocity (as velocity is the rate of change of displacement over time).

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12
Q

What is the gradient of velocity-time graphs?

A

In velocity-time graphs the gradient is the acceleration (as acceleration is the change of velocity divided by time).

The area below the line is the displacement.

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13
Q

What is the gradient of acceleration-time graphs?

A

Acceleration. The area below the line is the change in velocity.

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14
Q

Define a projectile.

A

An object moving through the air under the influence of only one force - gravity. The trajectory it will follow is a parabola.

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15
Q

Why is the path a projectile will take a parabola?

A

Because the vertical component of the velocity is constantly changing (due to the force of gravity) and the horizontal component of the velocity is constant (assuming no air resistance).

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16
Q

In reality, why will the trajectory of a projectile not be a parabola?

A

Because of air resistance. This will cause a shorter range, a lower max and a steeper gradient on the way down (i.e. the trajectory is not symmetric).

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17
Q

When is vertical and horizontal motion considered in projectile problems?

A

Vertical motion is considered when calculating the maximum height reached or the time of the flight. Horizontal motion is considered when calculating the range of the projectile.

18
Q

Give the formula to find the range in projectile problems.

A

Range = horizontal velocity x time

19
Q

Give the formula to find the initial velocity in projectile problems.

A

Initial velocity = √ Vh² + Vv²

20
Q

Give the initial vertical velocity and horizontal velocity for projectiles launched horizontally.

A

Initial vertical velocity: zero
Horizontal velocity: launch velocity, v

21
Q

Give the initial vertical velocity and horizontal velocity for projectiles launched at an angle above the horizontal.

A

Initial vertical velocity: vsinθ
Horizontal velocity: vcosθ

22
Q

Give the initial vertical velocity and horizontal velocity for projectiles launched at an angle below the horizontal.

A

Initial vertical velocity: vsinθ
Horizontal velocity: vcosθ

23
Q

What does the magnitude of fluid resistance depend on?

A
  • The velocity of the object relative to the fluid
  • The size and shape of the object
  • The fluid used (its viscosity)
24
Q

What is terminal velocity?

A

When the magnitude of the upwards air resistance is equal to the downwards gravitational force (weight) the object will no longer accelerate because the forces of the object are balanced. Its speed would remain constant, and this specific speed is called terminal velocity.

25
Q

Define mass.

A

The amount of matter in an object (m). Measured in kilograms (kg). It does not change with a change in position.

26
Q

Define weight.

A

The force of gravity acting on an object. Measured in newtons (N). It changes if an object changes its position.

27
Q

Give Newton’s First Law (Law of Inertia).

A

An object continues in uniform motion in a straight line or at rest unless a resultant external force acts.

28
Q

What is translational equilibrium?

A

If the resultant force on the object is zero, it is not accelerating and is said to be in translational equilibrium.

29
Q

Give Newton’s Second Law.

A

The resultant force on an object is proportional to the acceleration providing the mass of the object remains constant. F = ma

30
Q

Give Newton’s Third Law.

A

For every action on one object there is an equal but opposite reaction on another object.

31
Q

When the weight force on a slope is resolved into two forces what are they?

A

Parallel to a slope: mgsinθ
Perpendicular to a slope: mgcosθ

32
Q

What are the two types of solid friction?

A

Static friction: occurs when there is no relative motion between the surfaces.
Dynamic (kinetic) friction: occurs when there is relative motion between the surfaces.

33
Q

Define energy (E).

A

The capacity to do work. Measured in joules (J).

34
Q

Define work (W).

A

A transfer of energy. Measured in joules (J).

35
Q

Define power (P).

A

The rate at which work is done or energy is transferred. Measured in watts (W).

36
Q

Give the law of conservation of momentum.

A

The total linear momentum of a system remains constant provided no resultant external force acts.

37
Q

Define linear momentum (p).

A

The product of mass and velocity. It is a vector. Measured in kgms⁻¹ or Ns.

38
Q

Give the initial vertical velocity and horizontal velocity for projectiles launched at an angle below the horizontal.

A

Initial vertical velocity: vsinθ
Horizontal velocity: vcosθ

39
Q

What happens during an elastic collision?

A

No kinetic energy is lost. The total amount of energy remains constant. Momentum is conserved.

40
Q

What happens during an inelastic collision?

A

Kinetic energy is lost. The total amount of energy remains constant. Momentum is conserved.