Mechanics

Question 1

The horizontal component of a vector is given by ….

Answer 1

Fx= F cos θ

Question 2

The vertical component of a vector is given by….

Answer 2

Fy= F sin θ

Question 3

Vectors on an incline

Answer 3

Weight acts vertically downwards
Weight resolved along the plane = W cos θ
Weight resolved perpendicular to the plane = W sin θ

Question 4

Equilibrium

Answer 4

Resultant force = 0
Moment = 0

Question 5

Moments equation

Answer 5

Force x perpendicular distance between point to the line of action of the force

Question 6

Couples

Answer 6

Equal and opposite coplanar forces
(2 forces acting in opposite directions but equal, the same distance apart)

Question 7

Moment equation applied to couples

Answer 7

M=2Fd

Question 8

Principle of moments

Answer 8

Sum of the clockwise moments= sum of the anti-clockwise moments
Equilibrium -> not turning

Question 9

Centre of mass

Answer 9

Point at which weight appears to act

Question 10

Centre of mass hanging objects

Answer 10

COM directly below the point it is hung from

Question 11

Why do objects fall over?

Answer 11

Centre of mass is outside its base

Question 12

A object is stable when….

Answer 12

The centre of mass lies above its base

Question 13

Acceleration=

Answer 13

Rate of change of velocity

Question 14

Velocity=

Answer 14

Rate of change of displacement

Question 15

Displacement-time graphs

Answer 15

Gradient=v
Area under graph = distance
Instantaneous velocity -> tangent
Average velocity -> total displacement / time
acceleration = curve
constant gradient= constant acceleration

Question 16

Acceleration- time graphs

Answer 16

Non horizontal lines= non uniform acceleration
Gradient= rate of change of a
Area = change in velocity

Question 17

Velocity-time graphs

Answer 17

Area= displacement
Gradient= acceleration
curve= changing acceleration

Question 18

Determination of g by free fall

Answer 18

Steel ball bearing and trap door
electromagnet
Light gates or pressure sensitive plates
Measure from a range of heights
Plot a graph of t2 against h
g= 2x gradient

small ball bearing low air resistance
uncertainty of ruler 1mm

Question 19

Projectile motion

Answer 19

Horizontal v=u because a=0
Vertical u=0, a=-9.81

Question 20

Parabolic projectile motion

Answer 20

At maximum vertical displacement, Vy =0
Time = 1/2 t

Question 21

What is lift?

Answer 21

Upward force due to collisions with air particles

Planes push air downward during flight. Downward force on air particles, equal and opposite force upwards on wing

perpendicular to fluid flow -> shape of object causes fluid flowing over it to change direction

Question 22

Terminal velocity

Answer 22

Initial acceleration =-9.81 ms-2
Velocity increases, collisions per second increases, air resistance increases
Constant downward force
Terminal velocity #1 air resistance = weight
Maximum speed

Parachute deployment
Air resistance increases, deceleration, force due to air resistance decreases as velocity decreases, new terminal speed

Question 23

Shape of race cars

Answer 23

Streamlined so they can reach higher speed with the same driving force

Question 24

Newton’s first law

Answer 24

A body will continue in a state of rest or uniform motion in a straight line unless acted on by a net external force

Question 25

Newton’s second law

Answer 25

Σ F=Ma A body accelerates when acted on by net external force

Question 26

Newton’s third law

Answer 26

If object A exerts a force on object B. Then object B exerts a force on A that is equal in size and opposite in direction two sides of an interaction viewed from different perspectives same type classic non-example= book on table both forces act on book, not same type

Question 27

Impulse

Answer 27

Change in momentum

Question 28

Stable equilibrium

Answer 28

If a body is disturbed it tends to return to its original position

Question 29

Unstable equilibrium

Answer 29

If disturbed, a body tends to keep moving away from its original position

Question 30

Impulse equation

Answer 30

Impulse= force x time

Question 31

Conservation of momentum

Answer 31

Momentum before= momentum after recoil in explosions

Question 32

Elastic collisions

Answer 32

Momentum is conserved Kinetic energy is conserved

Question 33

Inelastic collisions

Answer 33

Momentum is conserved Kinetic energy is not conserved

Question 34

What type of collisions are explosions?

Answer 34

Inelastic

Question 35

Safety features

Answer 35

Air bags Seat belts Crumple zones Work by absorbing kinetic energy, increasing the time taken for a change in momentum to occur thus reducing force

Question 36

Work equation

Answer 36

W= Fd Where d is in the direction of the force

Question 37

Power definition

Answer 37

The rate of energy transfer

Question 38

Mass definition

Answer 38

Inertia, the ability of a body to resist acceleration by a net force greater mass = greater resistance to change in velocity

Question 39

Power equation

Answer 39

Force x velocity

Question 40

Gravitational potential energy definition

Answer 40

The work an object can do by virtue of its position in a gravitational field

Question 41

Kinetic energy

Answer 41

Work an object can do by virtue of its speed

Question 42

Energy

Answer 42

Is the stored ability to do work

Question 43

apparent weight

Answer 43

if an object subject to gravity is not in free fall, then there must be a reaction force to act in opposition to gravity

Question 44

examples of vector quantities

Answer 44

displacement, velocity, acceleration, force, momentum

Question 45

examples of scalar quantities

Answer 45

mass, temperature, distance, speed, energy

Question 46

free body diagrams

Answer 46

show all the forces acting on a body

Question 47

coplanar forces

Answer 47

multiple forces acting on a body in the same plane

Question 48

moments in the human body

Answer 48

effort acts against load force muscles, bones and joints act as levers where joints are the pivot

Question 49

stability

Answer 49

wide base, low centre of mass

Question 50

free fall motion

Answer 50

a=g

Question 51

all objects fall at the same rate

Answer 51

proof = inclined plane experiment slows fall + reduces effect of air resistance mass cancels

Question 52

W=Fd a note

Answer 52

F constant or average assume direction of force= direction of motion

Question 53

W=Fs a note

Answer 53

cannot be used for a variable force

Question 54

conservation of energy

Answer 54

energy cannot be created or destroyed only transferred, stored or dissipated total amount of energy in a closed system will not change

Question 55

friction in fluids

Answer 55

depends on viscosity

Question 56

area under Ft graph

Answer 56

impulse

Question 57

friction

Answer 57

force that opposes motion convert KE into heat and sound larger surface area= greater resistant force

Question 58

W= Fscosθ

Answer 58

calculating work when force acts in a different direction to the direction of motion

Question 59

ultrasound position detector

Answer 59

way of creating graphs of motion using a data logger which automatically records distance

Question 60

finding centre of mass lines of symmetry

Answer 60

intersection between lines of symmetry

Question 61

finding centre of mass irregular objects

Answer 61

hang from a point draw vertical line from point of suspension (plum bob) repeat from another point cross over of lines= centre of mass