Mechanics

Question 1

What is a scalar?

Answer 1

A quantity with magnitude only

Question 2

What is a vector?

Answer 2

A quantity with magnitude and direction

Question 3

What are free-body diagrams?

Answer 3

Diagrams which show a single body on its own with the forces which act on the body, but not the forces the body exerts

Question 4

How are forces resolved?

Answer 4

By splitting the force into horizontal and vertical components

Question 5

When is a force board in equilibrium?

Answer 5

When the ring is at the centre

Question 6

Define mass

Answer 6

The amount of matter in an object

Question 7

Define weight

Answer 7

The force experienced by a mass due to a gravitational field

Question 8

State the equation for weight

Answer 8

W = mg

Question 9

What is a moment?

Answer 9

The turning effect of a force around a turning point

Question 10

State the equation for moments

Answer 10

M(Nm) = F x d

Question 11

State the principle of moments

Answer 11

For a body to be in equilibrium, the sum of the clockwise moments about a point must equal the some of the anticlockwise moments about the same point

Question 12

What is a lever?

Answer 12

A rigid structure rotating around a pivot, in which an effort force works against the load force

Question 13

What are couples?

Answer 13

• A pair of coplanar (act on the same plane) forces of equal size which act parallel to each other but in opposite directions
• This produces a turning effect

Question 14

What is centre of mass?

Answer 14

The single point of an object that the whole weight can be considered to be concentrated

Question 15

State the suvat equations

Answer 15

• v = u + at
• s = ut + 1/2at²
• s = (u+v/2)t
• v² = u² + 2as
• S = vt - 1/2at²

Question 16

Define acceleration

Answer 16

The rate of change of an object’s velocity

Question 17

Define displacement

Answer 17

How far an object’s travelled from it’s starting point

Question 18

Define velocity

Answer 18

The rate of change of an object’s displacement

Question 19

Define speed

Answer 19

How fast an object is moving, regardless of direction

Question 20

How does increasing acceleration affect a displacement-time graph?

Answer 20

Gradient of the curve increases

Question 21

What does the gradient of a displacement-time graph represent?

Answer 21

The velocity

Question 22

What does the gradient of a velocity-time graph represent?

Answer 22

The acceleration

Question 23

How is uniform acceleration displayed on a velocity-time graph?

Answer 23

Constant gradient

Question 24

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

Answer 24

The displacement

Question 25

What does the area under the graph represent for a speed-time graph?

Answer 25

The distance travelled

Question 26

What part of an acceleration-time graph is decelerating?

Answer 26

Below the x-axis

Question 27

What does the area under an acceleration-time graph represent?

Answer 27

The total change in velocity

Question 28

State newton's first law of motion

Answer 28

An object will stay stationary or moving at a constant velocity unless acted upon by a resultant force

Question 29

State newton's second law of motion

Answer 29

F = ma, Force is directly proportional to the acceleration of the object

Question 30

State newton's third law of motion

Answer 30

- If two objects interact, they exert an equal and opposite force on each other - Equal = Magnitude of force, Type of force - Opposite = Direction of force

Question 31

What is freefall?

Answer 31

The motion of an object undergoing an acceleration of g

Question 32

State the freefall equations

Answer 32

- v = gt - v² = 2gs - s = 1/2gt² - s = vt/2

Question 33

What is projectile motion?

Answer 33

Motion with a constant horizontal velocity and a vertical velocity affected by acceleration due to gravity

Question 34

What is drag?

Answer 34

Friction caused by a fluid

Question 35

What is friction?

Answer 35

Force that opposes motion

Question 36

What are the energy transfers that occur due to friction?

Answer 36

Kinetic energy is turned into thermal energy

Question 37

What is lift?

Answer 37

An upward force on an object moving through a liquid

Question 38

Define terminal velocity

Answer 38

The velocity at which the driving force match the frictional force

Question 39

How is terminal velocity represented in a velocity-time graph?

Answer 39

The curve flattens at a certain velocity

Question 40

How is terminal velocity represented in an acceleration-time graph?

Answer 40

The acceleration = 0

Question 41

Describe the terminal velocity of a parachutist

Answer 41

- Leaves plane and accelerates due to gravity - Accelerates until air resistance = weight - Once close to ground, pulls parachute which increases air resistance - Slows parachutist until air resistance = weight - This terminal velocity is safe enough to land at

Question 42

Describe the velocity-time graph of a parachutist

Answer 42

- Velocity increases until it reaches a terminal velocity - Rapid drop in velocity until it reaches a new terminal velocity

Question 43

Define linear momentum

Answer 43

The product of an object's mass and velocity

Question 44

State the units of linear momentum

Answer 44

Kgm/s

Question 45

What is the principle of momentum?

Answer 45

Linear momentum is always conserved, assuming no external forces act

Question 46

What is an elastic collision?

Answer 46

A collision where momentum and kinetic energy are conserved

Question 47

Derive the equation for impulse

Answer 47

- F = ma and a = Δv/t - F = Δ(mv)/t - Ft = Δ(mv)

Question 48

Define impulse

Answer 48

The product of force and time which is equal to the change in momentum of an object

Question 49

Define work

Answer 49

The amount of energy transferred from one form to another when a force moves an object through a distance

Question 50

State the work done equation

Answer 50

W = Fs where s is distance moved, in m

Question 51

Define power

Answer 51

The rate of transfer of energy, in watts

Question 52

What does the area under a force-displacement graph represent?

Answer 52

The total work done

Question 53

State the equation of the power of a moving object with force acting at an angle

Answer 53

P = Fvcosθ

Question 54

State the principle of conservation of energy

Answer 54

Energy cannot be created or destroyed. It can be transferred to different forms but the total energy in the system won't change

Question 55

Define kinetic energy

Answer 55

The energy of anything moving

Question 56

Define potential energy

Answer 56

The energy gained by anything lifted

Question 57

Derive the equation for efficiency of a motor

Answer 57

- E = mgΔh - useful energy output - E = Pt = VIt = energy input - Efficiency = mgΔh/VIt

Question 58

What are the units for efficiency?

Answer 58

Efficiency has no units

Question 59

What is mechanical energy?

Answer 59

The sum of the kinetic energy and potential energy in a system

Question 59

What is mechanical energy?

Answer 59

The sum of the kinetic energy and potential energy in a system

Question 60

What are the 3 characteristics of projectile motion?

Answer 60

- Vertical and horizontal motion are separate - Motion is in a parabolic shape - Acceleration is in one plane only