Unit 1 - Kinematics And Dynamics Flashcards

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1
Q

Horizontal component velocity

A

U(h) = R*cosx°

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2
Q

Vertical component velocity

A

U(v) = R*sin°

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3
Q

Newton’s Universal Law of Gravitation

A

F = Gm(1)m(2)
————
r^2

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

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4
Q

Gravitational field strength definition

A

The gravitational force per kilogram or weight per unit mass

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5
Q

Inverse square nature of gravitational force

A

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

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

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6
Q

Why do satellites orbit?

A

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

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7
Q

Newton’s first law

A

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

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8
Q

Newton’s second law

A

Unbalanced forces accelerate masses

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9
Q

Newton’s third law

A

Each force exerts an equal and opposite reaction

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10
Q

If tension force and weight are balanced

A

At rest, constant upwards speed or constant speed downwards

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11
Q

If tension is greater than weight

A

Constant upward acceleration or constant downward acceleration

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12
Q

If weight is greater than tension

A

Constant downward acceleration

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13
Q

What must happen when calculating forces applied at an angle?

A

Get horizontal and vertical components

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14
Q

Equations for weight component

A

W(c) = WsinX°

Or

W(c) = mgsinX°

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15
Q

Equation for gravitational potential energy

A

E(p) = mgh

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16
Q

Equation for kinetic energy

A

E(k) = 1/2mv^2

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17
Q

Equation for work done

A

E(w) = Fd

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18
Q

What is momentum?

A

Product of mass and velocity:

p = mv

19
Q

What is the principle of conservation of linear momentum

A

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

20
Q

What is an elastic collision

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

Total kinetic energy conserved

21
Q

What is an inelastic collision?

A

More kinetic energy before collision

Most energy lost to heat

22
Q

What happens in an explosion?

A
One mass splits into two
Total E(k) increases
Total energy and momentum conserved
23
Q

Equations for impulse

A

Impulse = F(avg)*t(c)

Impulse = change in momentum

Impulse = mv-mu

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

Impulse = area under graph

24
Q

The effect of hardness of surface on impulse

A

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

25
Q

Find random uncertainty

A
Random uncertainty 
=
max-min
---------
      N
26
Q

Calculate percentage uncertainty

A
Percentage uncertainty 
=
Random Uncertainty
--------------------- * 100
             Mean
27
Q

What uncertainty do you use when calculating something

A

Biggest uncertainty in one of the variable

Same with percentage

28
Q

Analogue scales for uncertainties

A

Far apart divisions = 1/5

Close divisions = 1/2

29
Q

Digital scale for uncertainties

A

Always +/-1 of the last digit

Eg 9.98 would be +/-0.01

30
Q

Systematic uncertainties

A

Give consistently too high or too low reading

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

31
Q

What happens during the Doppler effect

A

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

32
Q

Doppler effect when source is moving towards observer

A

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

33
Q

Doppler effect when source is moving away from observer

A

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

34
Q

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

A

Away = add

35
Q

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

A

Towards = take away

36
Q

Equation for Hubble’s constant

A

v = Hd

recession velocity = hubble’s constant * distance

Hubble’s constant = 2.3*10^-18s^-1

37
Q

Redshift equations

A

z=v/c

Redshift = recession velocity / speed of light

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

38
Q

How can the age of the universe be calculated?

A

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

t = 1 / Hubble’s constant

39
Q

Evidence for the Big Bang

A

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

40
Q

What is dark energy?

A

Fuels the expansion of the universe

41
Q

What is dark matter?

A

Not detected easily as it weakly interacts with detectors

42
Q

Evidence for dark matter?

A

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

43
Q

How do you calculate temperature of stellar objects?

A

By plotting intensity of radiation against wavelength

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