Mechanics

Question 1

What is a Scalar ?

Answer 1

have only magnitude (size)

Question 2

What is a Vector ?

Answer 2

have both magnitude and direction

Question 3

How to add vectors ?

Answer 3

can add together by either scale drawing or trigonometry

Question 4

What is Displacement (s) ?

Answer 4

is how far an object has travelled from its starting position in a given distance
- Measured in m

Question 5

What is Velocity (v) ?

Answer 5

is the rate of change of displacement over time

- Measured in ms^-1

Question 6

What is Acceleration (a) ?

Answer 6

is the rate of change of velocity over time

• Measured in ms^-2
• can be change in direction two

Question 7

How to resolve a vector ?

Answer 7

Horizontal Component =
V x COSѲ
Vertical Component = 
V x SINѲ
- at an right angle

Question 8

What is Equilibrium ?

Answer 8

a object is in Equilibrium if all objects acting on an object cancel each other out (resultant force=0)
- can be drawn as a closed triangle (3forces)

Question 9

Displacement - time graphs ?

Answer 9

the gradient is the velocity = Δs/Δt

- can be parabola

Question 10

Velocity - time graphs ?

Answer 10

the gradient is the acceleration = Δv/Δt

the area under the graph is the displacement

Question 11

Acceleration - time graphs ?

Answer 11

the area under the graph is the velocity

Question 12

What is Newton’s First law ?

Answer 12

that a body will remain at rest or at a constant velocity in a straight line unless acted on by an unbalanced/external force

Question 13

What is Newton’s Second law ?

Answer 13

the acceleration is proportional to the resultant force acting on it , in the direction of the force
- F = m x a

Question 14

What is Newton’s Third law ?

Answer 14

when body A exerts a force on body B, body B exerts a equal bot opposite force on A

Question 15

What is Force ?

Answer 15

is the rate of change of momentum over time

F = mv/t

Question 16

What does all the objects in free fall have ?

Answer 16

they have the same acceleration due to gravity (g) - 9.81ms^-2

• force acting = weight
• acceleration is independent of mass ( no air resistance)
• a1=g + a2=g

Question 17

When to use the SUVAT equations ?

Answer 17

when their in a constant/uniform acceleration

Question 18

What is Projectile motion ?

Answer 18

with horizontal and vertical components but are independent of each other
- ignore air resistance

Question 19

Projectile motion calculations ?

Answer 19

do the vertical section first 
VERTICAL 
- acceleration = 9.81
- velocity change with time V = U + at
HORIZONTAL 
- acceleration = 0
- velocity is constant (u=v)

Question 20

What is Terminal Velocity ?

Answer 20

air resistance (drag force) equals in magnitude the weight of the falling object

Question 21

How is Terminal Velocity reached ?

Answer 21

1) the driving force (WEIGHT) is much bigger than the drag force due to acceleration
2) as the speed increases the resistance force increases
3) the resultant force = 0 so constant velocity (TV)

Question 22

Terminal Velocity linked to parachute ?

Answer 22

when the parachute is released the resistance force > weight force so slow down till terminal velocity reached again

Question 23

What affects the size of drag force ?

Answer 23

drag force increases with speed and surface area

Question 24

What is Friction ?

Answer 24

is a force which opposes motion

• cannot speed up/move things
• covert kinetic into heat energy
  1) Contact
  2) drag

Question 25

Vectors on a slope ?

Answer 25

- reaction force perpendicular to slope - WCOSѲ = down - WSINѲ = across slope

Question 26

What is Work (W) ?

Answer 26

is multiplying force by the displacement in the direction of the force W = FsCOSѲ - Measured in Joules (J)

Question 27

When is work done ?

Answer 27

whenever energy is transferred | - area under F/s graph

Question 28

What is Power ?

Answer 28

is the rate of change of energy transfer or the work-done per second P = ΔW/Δt P = Fv - Measured in Watts (w) or JS^-1

Question 29

What is the principle of conservation of energy is ?

Answer 29

that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another Ek = Ep

Question 30

How to find the efficacy of a machine ?

Answer 30

- Useful-Output power/Input power | - x100 = %

Question 31

What is Momentum (p) ?

Answer 31

mass multiply by its velocity p = mv - Measured in kgms^-1 or Ns^-1 - always conserved

Question 32

What is an elastic collision ?

Answer 32

Both momentum and kinetic energy is conserved

Question 33

What is an Inelastic collision ?

Answer 33

Momentum is conserved but kinetic energy is NOT conserved - transfer to different form of energy F = mv/t - constant velocity = m/t means flow rate / kgs^-1

Question 34

What is Impulse ?

Answer 34

FΔt = Δmv - change in momentum - e.g. Δt on trampoline is long to reduce F ( so reduce Ek) - area under F/t graph

Question 35

Examples of car safety - impulse ?

Answer 35

- crumple zone - seat belt - air bag

Question 36

How to find Kinetic energy ?

Answer 36

Ek = 1/2mv^2

Question 37

How to find change in gravitational Potential energy ?

Answer 37

ΔEp = mgΔh

Question 38

What energy is transferred when an object falls or climbs ?

Answer 38

``` CLIMBS - potential increase - kinetic decrease FALLS - potential decrease - kinetic increase ```

Question 39

What is a Moment ?

Answer 39

is the force x perpendicular distance from the pivot = Fd - Measured in Nm

Question 40

What are the principles of moments ?

Answer 40

it states the total clockwise moments is equal to the total anti-clockwise moments about any point CW = ACW

Question 41

What is a couple ?

Answer 41

a pair of equal forces in opposite direction M = Fd - torque of couple - one of the forces x perpendicular distance between forces - causes turning effect - same distance from pivot

Question 42

What is the centre of mass of an object ?

Answer 42

The single point that can be consider the whole weight of object to act from