ODU

Question 1

State the definition of acceleration

Answer 1

acceleration is the rate of change of velocity

Question 2

the gradient of an s-t graph gives…

Answer 2

velocity

Question 3

the gradient of a v-t graph gives…

Answer 3

acceleration

Question 4

the area under a v-t graph gives…

Answer 4

displacement

Question 5

the area under an a-t graph gives…

Answer 5

velocity

Question 6

how do you know that the vector on a motion-time graph has started acting in the opposite direction?

Answer 6

The graph crosses the time axis

Question 7

explain satellite motion

Answer 7

the satellite is in freefall around a planet. It follows a circular path because it has a constant velocity at a tangent to the planet and a constant acceleration towards the planet. The projectile does not it the planet because it has velocity at a tangent to the planet’s surface.

Question 8

Projectiles have constant horizontal ________ and constant vertical ________ in the absence of friction

Answer 8

Projectiles have constant horizontal velocity and constant vertical acceleration in the absence of friction

Question 9

Always consider _______ and ________ components separately

Answer 9

Always consider horizontal and vertical (i.e. perpendicular) components separately

Question 10

state newton’s first law

Answer 10

newton’s first law states that an object at rest will remain at rest and an object in motion will remain in motion with constant velocity unless acted upon by an unbalanced force

Question 11

State a corollary of newton’s first law (just checking you know the implications of newton 1)

Answer 11

an object will accelerate when acted upon by an unbalanced force

Question 12

state what is meant by the phrase “balanced forces”

Answer 12

forces have the same size but opposite direction (i.e. there is no net force on an object)

Question 13

state newton’s second law

Answer 13

the vector sum of forces on an object is equal to the product of the mass and acceleration of an object i.e. ΣF = ma

Question 14

State newton’s third law

Answer 14

Every action force has an equal and opposite reaction force. Remember: The action and reaction force act on different objects. Newton 3 applies to interaction between objects

Question 15

state what is meant by “friction”

Answer 15

Friction is a force which opposes the motion of an object

Question 16

state what is meant by “tension”

Answer 16

Tension is a force which is transmitted from one object to another via a coupling. It acts in opposite directions on each object

Question 17

State what is meant by “terminal velocity”

Answer 17

terminal velocity is the maximum velocity of an object in freefall when friction is taken into account. It happens when weight = -friction

Question 18

What does the reading on a scale calibrated in newtons tell you?

Answer 18

the normal reaction force

Question 19

Explain why the reading on a scale changes when in a lift

Answer 19

w = mg acts downwards and doesn’t change. N is the normal reaction force. This changes depending on the acceleration of the lift: ΣF = ma => N-mg = ma. The scales show N.

Question 20

State the equation for calculating the component of an object’s weight acting down a slope

Answer 20

mgsin(θ)

Question 21

State the equation for calculating the component of an object’s weight perpendicular to a slope

Answer 21

mgcos(θ)

Question 22

State the law of conservation of momentum

Answer 22

The total momentum before a collision/explosion is equal to the total momentum after a collision/explosion in the absence of external forces

Question 23

State what is meant by the term “elastic collision”

Answer 23

Both kinetic energy and momentum are conserved

Question 24

State what is meant by the term “inelastic collision”

Answer 24

Momentum is conserved but kinetic energy is not

Question 25

How is impulse calculated from a force-time graph?

Answer 25

By finding the area under the graph

Question 26

State two equations for impulse

Answer 26

Impulse = Ft and Impulse = mv - mu

Question 27

Explain how the force of an impact can be reduced

Answer 27

By increasing the time of the collision i.e. increasing t in F = (mv - mu)/t. t goes up, F goes down

Question 28

When calculating the force of gravitational attraction between two masses, between where is their separation measured?

Answer 28

The centres of the masses

Question 29

State Einstein's postulates

Answer 29

1. The laws of physics are the same in all inertial reference frames. 2. The speed of light is constant in all inertial reference frames and independent of the motion of its source

Question 30

State what is meant by the term "time dilation"

Answer 30

Time dilation is the increase in time for an event occurring in a moving frame as measured by a stationary observer. t' = dilated time

Question 31

Identify the symbols t, t', l and l'

Answer 31

t=proper time, t'=dilated time, l=proper length, l'=contracted length

Question 32

Describe the Doppler Effect

Answer 32

The frequency of sound emitted by a moving source is observed to increase when it approaches an observer and fall as it moves away

Question 33

Explain the Doppler Effect

Answer 33

Frequency increases on approach because the source catches up with the sound it is emitting, meaning that the wave peaks are closer together and the frequency increases. Frequency decreases as the source moves away because the source moves away from the sound it emits, stretching the wave peaks apart and decreasing its frequency.

Question 34

In the equation for Doppler Effect, do you use a + sign when the source is coming towards you or moving away from you?

Answer 34

Moving away. Putting a + sign makes the denominator bigger and therefore the observed frequency smaller, which happens when the source moves away from the observer.

Question 35

When a source of sound waves is moving towards you, do you observe a higher or lower frequency?

Answer 35

Higher because the waves become bunched up and the frequency increases

Question 36

State 4 pieces of evidence to support the Big Bang theory and universal expansion.

Answer 36

CMBR, the relative abundances of hydrogen and helium, the darkness of the night sky, the large number of galaxies showing redshift rather than blueshift

Question 37

How can the mass of a galaxy be estimated?

Answer 37

By measuring the orbital velocity of stars and using newton's law of gravitation

Question 38

Why does the high orbital velocity of stars near the edges of galaxies provide evidence for the existence of dark matter?

Answer 38

The orbital velocities of stars within a galaxy does not reduce as one might expect, rather it increases the eventually levels off. This suggests that there is matter which we cannot see located at the outer edges of a galaxy

Question 39

State one piece of evidence for the existence of dark matter

Answer 39

The orbital velocities of stars within a galaxy is larger than expected due to all visible matter. This leads us to calculate the masses of galaxies which are much larger than can be accounted for by visible matter and suggests the existence an some unseen, dark matter.

Question 40

State one piece of evidence for the existence of dark energy

Answer 40

The accelerating rate of expansion of the universe

Question 41

As the temperature of a star increases, what happens to the peak wavelength at which it emits light?

Answer 41

It gets shorter

Question 42

Which object will emit more radiation per unit surface area per unit time: a hot one or a cold one?

Answer 42

A hot one

Question 43

How does the distribution of radiation emitted by a star change as its temperature increases?

Answer 43

Hotter objects emit more radiation at all wavelengths than colder ones and the peak wavelength at which they emit radiation decreases

Question 44

What is an order of magnitude?

Answer 44

It is a power of 10

Question 45

State what is meant by the term "fermion"

Answer 45

A fermion is a matter particle

Question 46

State what is meant by the term "boson"

Answer 46

A boson is a force mediating particle

Question 47

Quarks are ______

Answer 47

fermions (i.e. matter particles)

Question 48

Leptons are ________

Answer 48

fermions (i.e. matter particles)

Question 49

List the 6 quarks

Answer 49

Up down strange charm top bottom

Question 50

List the 6 leptons

Answer 50

electron, muon, tau, electron neutrino, muon neutrino, tau neutrino

Question 51

List the 4 force mediating particles and their associated force

Answer 51

Photon (electromagnetic force), Z & W+- bosons (weak force), gluon (strong force)

Question 52

Which force is missing from the Standard Model

Answer 52

Gravity

Question 53

What is the standard model?

Answer 53

A model of fundamental particles and their interactions

Question 54

What are hadrons made up of?

Answer 54

Hadrons are composite particles made of quarks

Question 55

Baryons are a type of ________ and they are therefore made-up of ________

Answer 55

hadron, quarks

Question 56

Mesons are a type of ________ and they are therefore made-up of ________

Answer 56

hadron, quarks

Question 57

Baryons are made of _______ quarks

Answer 57

3

Question 58

Mesons are made of…

Answer 58

a quark-antiquark pair

Question 59

Describe beta decay and how it is evidence for the existence of the neutrino

Answer 59

beta decay is when a neutron turns into a proton, electron and an anti electron neutrino. The mass after beta decay was much smaller than could be accounted for by mass-energy conversion and pointed to the existence of a new particle, the neutrino

Question 60

State what is meant by "anti-matter"

Answer 60

Every particle in the standard model has a corresponding anti-particle, identical in every way except charge. These particles are called "anti-matter".

Question 61

State one piece of evidence for the existence of antimatter.

Answer 61

When matter meets antimatter they annihilate