MECHANICS

Question 1

work

Answer 1

work is done when a force moves an object through a distance
work = force x distance
W = fd

Question 2

energy

Answer 2

the ability to do work

Question 3

the principle of conservation of energy

Answer 3

states that energy cannot be created or destroyed, but can only be converted from one form to another

Question 4

kinetic energy

Answer 4

the energy a body has due to its motion

Ek = 1/2mv^2

Question 5

potential energy

Answer 5

the energy a body has due to its height or position

Ep = mgh

Question 6

mass

Answer 6

mass should be treated as a form of energy. the energy contained within a mass, m is given by
E = mc^2
a measure of how difficult it is to accelerate that body

Question 7

power

Answer 7

1. the rate at which work is done
2. the rate at which energy is converted from one form into another
   power = energy / time

Question 8

efficiency

Answer 8

efficiency = output / input x 100

Question 9

scalar

Answer 9

only have magnitude

e.g. mass, length, time

Question 10

vector

Answer 10

have both magnitude and direction

e.g. velocity, acceleration, displacement

Question 11

measurement of velocity and acceleration

Answer 11

ticker-tapes or light gates

Question 12

velocity time graph

Answer 12

slope = acceleration

area under graph = distance travelled

Question 13

speed

Answer 13

the rate of change of distance with respect to time

Question 14

displacement

Answer 14

distance in a given direction

Question 15

velocity

Answer 15

the rate of change of displacement with respect to time

Question 16

acceleration

Answer 16

the rate of change of velocity with respect to time

Question 17

equations of motion

Answer 17

1. v = u+at
2. s = ut + 1/2 at^2
3. v^2 = u^2 + 2as

Question 18

force

Answer 18

anything that causes an acceleration

Question 19

the newton

Answer 19

the force that gives a mass of 1kg an acceleration of 1ms^-2

Question 20

weight

Answer 20

the force of the earths gravity acting on an object

Question 21

newtons 1st law of motion

Answer 21

every body will remain in a state of rest or travelling with a constant velocity unless an unbalanced force acts on it

Question 22

newtons 2nd law of motion

Answer 22

when an unbalanced force acts on a body the rate of change of the bodys momentum is directly proportional to the force and takes place in the direction of the force

Question 23

newtons 3rd law of motion

Answer 23

if body A exerts a force on body B, the body B exerts an equal but opposite force on body A. i.e action and reaction are equal but opposite

Question 24

force & momentum

Answer 24

F = mv-mu/t i.e. force is equal to the rate of change of momentum

Question 25

momentum

Answer 25

the product of a bodys mass and velocity | p = mv

Question 26

friction

Answer 26

a force which tends to oppose motion.

Question 27

principle of conservation of momentum

Answer 27

states that in any interaction between bodies, the total momentum before the interaction will equal the total momentum after the interaction, provided no external forces act upon the bodies. m1u1 + m2u2 = m1v1 + m2v2

Question 28

density

Answer 28

the density of an object is its mass per unit volume

Question 29

pressure

Answer 29

force per unit area | pressure = force / area

Question 30

pascal (Pa)

Answer 30

1 pascal = 1 newton per square metre

Question 31

pressure in a liquid

Answer 31

``` P = pgh h = depth of water g = acceleration due to gravity p = density ```

Question 32

archimedes principle

Answer 32

states that when an object is partially or completely immersed in a fluid it experiences an upthrust equal in magnitude to the weight of the fluid displaced

Question 33

law of flotation

Answer 33

states that the weight of a floating body is equal to the weight of the fluid it displaces

Question 34

boyles law

Answer 34

states that at constant temperature the volume of a fixed mass of gas is inversely proportional to its pressure

Question 35

newtons law of universal gravitation

Answer 35

states that any two point masses in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. F = Gm1m2/d^2 G = universal gravitational constant

Question 36

circular motion

Answer 36

an object in circular motion has a linear velocity, v, and an angular velocity ω = θ/t

Question 37

period

Answer 37

T = 2π / ω

Question 38

centripetal acceleration

Answer 38

the acceleration of a body in circular motion. its direction is towards the centre of the circle a = rω^2 // a= v^2/r

Question 39

centripetal force

Answer 39

the force on a body in circular motion. its direction is towards the centre of the circle. the reaction to this force is away from the centre of the circle and is known as the centrifugal force

Question 40

simple harmonic motion

Answer 40

any motion where the acceleration (a) of a particle is proportional to its distance (s) from an equilibrium position a = -ω^2s

Question 41

hookes law

Answer 41

states that when an object is bent, stretched or compressed by a displacement s, the restoring force f is directly proportional to the displacement - provided the elastic limit is not exceeded. F = -ks

Question 42

moment of a force

Answer 42

the moment of a force about an axis is equal to the magnitude of the force multiplied by the perpendicular distance from the axis to the line of action of the force

Question 43

couple

Answer 43

created by two parallel forces with the same magnitude acting in opposite directions

Question 44

conditions for equilibrium

Answer 44

1. the sum of the force in any direction equals the sum of the forces in the opposite direction 2. the sum of the moments about any point is zero

Question 45

explain the distinction between speed and velocity

Answer 45

velocity is speed in a given direction

Question 46

acceleration due to gravity

Answer 46

it is the acceleration of an object which is in freefall due to the gravitational pull of the earth

Question 47

why does the value of g, the acceleration due to gravity, vary at different locations on the surface of the earth?

Answer 47

locations are at different distances from the earth's centre

Question 48

why is the acceleration due to gravity on the moon less than on earth

Answer 48

the mass of the moon is less than the mass of the earth

Question 49

forces acting on a cheetah when its running

Answer 49

air resistence, gravity friction

Question 50

instrument used to measure pressure

Answer 50

barometre

Question 51

factors which effect the size of the gravitational force between two bodies

Answer 51

mass of the objects | distance between them

Question 52

relationship between acceleration due to gravity, g and the distance from the centre of the earth

Answer 52

g is proportional to 1/d^2

Question 53

why is it easier to turn a nut using a longer spanner than a shorter one

Answer 53

the distance from the fulcrum is greater therefore there is a greater turning effect

Question 54

factors on which the potential energy of a body depends

Answer 54

mass acceleration due to gravity height

Question 55

why is a fluorescent tube an efficient source of light

Answer 55

most of the electrical energy s converted to light energy

Question 56

relationship between the period of the moon and the radius of its orbit

Answer 56

the period squared is proportional to the radius cubed

Question 57

A body is said to be moving with simple harmonic motion if:

Answer 57

I. It’s acceleration is directly proportional to its distance from a fixed point on its path II. It’s acceleration is always directed towards that point