Unit 1 - Kinematics And Dynamics

Question 1

Horizontal component velocity

Answer 1

U(h) = R*cosx°

Question 2

Vertical component velocity

Answer 2

U(v) = R*sin°

Question 3

Newton’s Universal Law of Gravitation

Answer 3

F = Gm(1)m(2)
————
r^2

G = gravitational constant (6.67*10^-11m^3kg^-1s^-2)

Question 4

Gravitational field strength definition

Answer 4

The gravitational force per kilogram or weight per unit mass

Question 5

Inverse square nature of gravitational force

Answer 5

As the distance between two masses increase, the gravitational force decreases

As it doubles, force quarters
As it triples, force is 1/9th etc

Question 6

Why do satellites orbit?

Answer 6

Gravitational force exerted on satellite
Force accelerates the satellite
Orbital speed is constant, but velocity vector changes direction
Satellite follows curved path that follows the curvature of the Earth

Question 7

Newton’s first law

Answer 7

Balanced forces mean the object will be at rest or constant velocity

Question 8

Newton’s second law

Answer 8

Unbalanced forces accelerate masses

Question 9

Newton’s third law

Answer 9

Each force exerts an equal and opposite reaction

Question 10

If tension force and weight are balanced

Answer 10

At rest, constant upwards speed or constant speed downwards

Question 11

If tension is greater than weight

Answer 11

Constant upward acceleration or constant downward acceleration

Question 12

If weight is greater than tension

Answer 12

Constant downward acceleration

Question 13

What must happen when calculating forces applied at an angle?

Answer 13

Get horizontal and vertical components

Question 14

Equations for weight component

Answer 14

W(c) = WsinX°

Or

W(c) = mgsinX°

Question 15

Equation for gravitational potential energy

Answer 15

E(p) = mgh

Question 16

Equation for kinetic energy

Answer 16

E(k) = 1/2mv^2

Question 17

Equation for work done

Answer 17

E(w) = Fd

Question 18

What is momentum?

Answer 18

Product of mass and velocity:

p = mv

Question 19

What is the principle of conservation of linear momentum

Answer 19

The total momentum before a collision or explosion is equal to the total momentum after a collision or explosion when there are no external forces like friction

Question 20

What is an elastic collision

Answer 20

Total E(k) before 
=
Total E(k) after

Total kinetic energy conserved

Question 21

What is an inelastic collision?

Answer 21

More kinetic energy before collision

Most energy lost to heat

Question 22

What happens in an explosion?

Answer 22

One mass splits into two
Total E(k) increases
Total energy and momentum conserved

Question 23

Equations for impulse

Answer 23

Impulse = F(avg)*t(c)

Impulse = change in momentum

Impulse = mv-mu

F(avg)*t(c) = mv-mu

Impulse = area under graph

Question 24

The effect of hardness of surface on impulse

Answer 24

Softer surfaces increase contact time which results in the average force being less if change in momentum is the same

Question 25

Find random uncertainty

Answer 25

Random uncertainty 
=
max-min
---------
      N

Question 26

Calculate percentage uncertainty

Answer 26

Percentage uncertainty 
=
Random Uncertainty
--------------------- * 100
             Mean

Question 27

What uncertainty do you use when calculating something

Answer 27

Biggest uncertainty in one of the variable

Same with percentage

Question 28

Analogue scales for uncertainties

Answer 28

Far apart divisions = 1/5

Close divisions = 1/2

Question 29

Digital scale for uncertainties

Answer 29

Always +/-1 of the last digit

Eg 9.98 would be +/-0.01

Question 30

Systematic uncertainties

Answer 30

Give consistently too high or too low reading

Eg scale that isn’t reading 0 before you weigh something

Question 31

What happens during the Doppler effect

Answer 31

Sounds waves propagate outwards from the source at 340ms^-1 (in air)

Question 32

Doppler effect when source is moving towards observer

Answer 32

Source is moving towards so waves bunch closer together and therefore the source is heard to be higher pitched

Question 33

Doppler effect when source is moving away from observer

Answer 33

Source is moving away so waves spread further apart and therefore the source is heard to be lower pitched

Question 34

What sign do we use when the source is moving away?

Answer 34

Away = add

Question 35

What sign do we use when the source is moving towards the observer?

Answer 35

Towards = take away

Question 36

Equation for Hubble’s constant

Answer 36

v = Hd

recession velocity = hubble’s constant * distance

Hubble’s constant = 2.3*10^-18s^-1

Question 37

Redshift equations

Answer 37

z=v/c

Redshift = recession velocity / speed of light

z = observed wavelength - rest wavelength
————————————-
rest wavelength

Question 38

How can the age of the universe be calculated?

Answer 38

Rewinding the expansion process back to a singularity at the start of the universe

t = 1 / Hubble’s constant

Question 39

Evidence for the Big Bang

Answer 39

Expanding universe

Most galaxies redshifted

Rewinding expansion leads to singularity that contained everything in universe

Cosmic microwave background radiation- the “after glow” of the Big Bang

Abundance of hydrogen and helium as these were most likely to form as universe cooled from Big Bang

Question 40

What is dark energy?

Answer 40

Fuels the expansion of the universe

Question 41

What is dark matter?

Answer 41

Not detected easily as it weakly interacts with detectors

Question 42

Evidence for dark matter?

Answer 42

Rotational speeds of galaxies requires a bigger gravitational force than can be accounted for by mass detected

Gravitational lensing - light is affected by dark matter which explains some astronomical explanations

Question 43

How do you calculate temperature of stellar objects?

Answer 43

By plotting intensity of radiation against wavelength

Peak wavelength * temperature in kelvin = constant (2.9*10^-3)