PHYSICS EOY Flashcards

Question

How do you calculate the amount of energy transferred to or released from an object when its temperature changes? [you do not need to learn this equation, just be able to use it]

Answer 1

Change in energy = mass × specific heat capacity x change in temperature ΔE = mcΔΘ Energy (Joules, J), Mass (kilograms, kg), Specific heat capacity (J/kg°C),Change in temp (°C or Kelvin, K)

Answer 2

The specific heat capacity of a substance is the energy (in J) needed to increase the temperature of 1 kg of a substance by 1 0C (or Kelvin can be used too)

Answer 3

The mass of the metal block is measured using a balance. The immersion heater is connected to a power supply and transfers energy to the block, this energy is measured using a joulemeter. The insulation reduces the amount of energy that is transferred to the surroundings, this reduces uncertainty in the value for the specific heat capacity. The specific heat capacity is calculated by: Specific heat capacity = energy transferred / mass x change in temperature

Answer 4

Accurate data is data which is close to the true value

Answer 5

Precise data is data in which repeated measurements show very little spread about the mean value.

Answer 6

If another person can get the same result with the same, or different method/equipment, then the data is reproducible

Answer 7

If the same person can get the same result with the same equipment and method then the data is repeatable.

Answer 8

Random uncertainty causes measurements to be spread around a mean value. The effect of random uncertainty can be reduced by repeating and averaging data.

Answer 9

Systematic uncertainty occurs when measurement is always too high or too low for each repeat. Usually because of an error in the equipment e.g a badly calibrated thermometer.

Answer 10

This is a type of systematic uncertainty which occurs when a measuring instrument reads a value when it should say zero. E.g. a mass balance which doesn’t say zero when there is nothing on it.

Answer 11

Unwanted thermal energy transfers can be reduced e.g. by lubrication (when parts move) and thermal insulation

Answer 12

The thermal conductivity of a material tells us the rate at which energy is transferred through the material when there is a temperature difference either side of it.

Answer 13

The rate of cooling of an object is the temperature decrease per second.

Answer 14

The thickness of the building’s walls and the thermal conductivity of its insulation affect the rate of cooling.

Answer 15

The specific latent heat of a substance is the amount of energy (in J) required to change the state of 1 kg of the substance with no change in temperature. The specific latent heat of fusion is the amount of energy required to change the state of 1 kg of a substance from solid to liquid with no change of temperature. The specific latent heat of vaporisation is the amount of energy required to change the state of 1 kg of a substance from liquid to gas with no change of temperature.

Answer 16

Energy = mass × specific latent heat E = mL Energy (Joules, J), Mass (kilograms, kg), Specific latent heat (J/kg)

Answer 17

https://docs.google.com/presentation/d/1Nt6WjzkjZQozAkgYdbGiBGni74KMnT_lOWIhWA2V-_4/edit?slide=id.p#slide=id.p

Answer 18

Our solar system contains: ● The Sun (a star) ● Eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) ● Dwarf planets (Pluto, Ceres and Eris are some examples) ● Natural Satellites (Moons) ● The asteroid belt (this exists between Mars and Jupiter) ● Comets are frozen rocks that move around the Sun in often very elliptical orbits

Answer 19

Our solar system is in the Milky Way galaxy, a collection of around 100 billion stars.

Answer 20

The Sun formed about 4.5 billion years ago when a cloud of gas and dust (a nebula) was pulled together by gravitational attraction. The particles in the cloud got faster and collided more. The gas warmed up and eventually became hot enough to glow. This was a protostar. As the protostar gets more dense, more collisions take place and it gets hotter. Eventually the cloud gets hot enough for hydrogen atoms to fuse, forming helium. We call a star in this state a main sequence star.

Answer 21

In the main sequence stage, the gravitational attraction still pulling on the gas (actually a plasma) is balanced by the outward force of the radiation from the nuclear fusion in the core. We say the forces are in equilibrium.

Answer 22

Uranium and other such heavy elements naturally present on Earth can only be formed in a supernova explosion so the Sun must have formed from the remnants of a supernova.

Answer 23

When a star starts to run out of hydrogen to fuse, its core collapses and the outer layers swell, cool down and the star will become a red giant. Here, helium and other light elements in the core fuse to form heavier elements. When there are no more light elements in the core, fusion stops and no more radiation is released. The star collapses, and as it does it turns from red to yellow to white becoming a white dwarf (much smaller than it was before). Such stars eventually fade out becoming black dwarfs.

Answer 24

Stars much bigger than ours become red supergiants then they collapse. Because there is more mass the collapse is more violent and a supernova explosion occurs. This is where elements heavier than iron can form from fusion. The explosion compresses the core into a neutron star, an extremely dense object made only of neutrons. If the original star was massive enough, it becomes a black hole instead of a neutron star. The gravitational field of a black hole is so strong nothing can escape from it, not even light. https://docs.google.com/presentation/d/1ofQbVNSHSjPPuzZG-o81mxvATsy7SuTw6kQGiygKyek/edit?slide=id.p#slide=id.p

Answer 25

A planet orbits a star, enough gravity to make it spherical and sweeps out its own orbital path of other smaller objects. A moon orbits a planet. A satellite is something that orbits something else. The Moon is a natural satellite. There are many artificial (man-made) satellites.

Answer 26

Gravity. It is an example of a centripetal force because it is acting towards the centre of a circle.

Answer 27

An object orbits another at a constant speed. Its direction is constantly changing so its velocity is changing (speed in a given direction). Therefore we say the object is accelerating towards the centre of the circle. The acceleration is a change of velocity per second.

Answer 28

If an object in orbit slows down, it will fall into a lower orbit (closer to the Earth). If it gets too slow, it will crash to the surface. If an object in orbit speeds up, it will move to a higher orbit (further from the Earth). If it gets sufficiently fast it will escape the gravitational pull of the object it is orbiting and fly off into space. At the correct speed an object will orbit at a constant height and speed.

Answer 29

Light waves are stretched out if a star or galaxy is moving away from an observer. The wavelength of the light increases.This is called red-shift because the light is shifted towards the longer wavelength red end of the visible spectrum. If a star or galaxy was moving towards the observer, the light waves would be compressed making the wavelength shorter and we would say the light has been blue-shifted.

Answer 30

The faster a star or galaxy is moving away from an observer, the greater the effect of red-shift. Red-shift is observed in the large majority of galaxies so they are moving away from us and the more distant ones are moving away faster (speed of recession). Edwin Hubble suggested that this meant that the universe is expanding because everything is moving away from everything else.

Answer 31

The universe is expanding and originated as a very small and extremely hot and dense region. Red-shift provides evidence for this theory because at some point earlier in time the light must have been extremely short wavelength (high energy) and everything moving apart suggests everything came from one centralised region.

Answer 32

In 1965 scientists discovered microwaves coming from every direction in space. This microwave radiation had been red-shifted suggesting that 13.5 (ish) billion years ago there must have been a massively energetic event in one place to still have evidence of it today. This radiation was called the Cosmic Microwave Background Radiation (CMBR).

Answer 33

The Steady State theory suggested that the universe was expanding, but it had always been there and matter was created into the spaces that the universe expanded into. More evidence was present for the Big Bang theory so that is why it is widely accepted today as being the most probable origin story for the universe.

Answer 34

Depending on the total mass of matter in the universe (unknown because we still have not observed dark matter, a strange substance that is needed for galaxies to maintain their shape) the universe could: 1. [If the universe is less dense than a certain amount] Expand forever, the stars will gradually die out and the universe will cool (Big Yawn) 2. [If the universe is more dense than a certain amount] Stop expanding and collapse (Big Crunch) - Some scientists currently think the universe has gone through cycles of this.

Answer 35

If a graph is plotted and the line of best fit is straight then we say that there is a linear relationship between the two quantities on the x and y axes. If the line is not straight then it is non-linear.

Answer 36

If a graph is plotted and the line of best fit is straight and goes through the origin then there is a directly proportional relationship between the two quantities.

Answer 37

The spring constant is the amount of force needed to stretch (or compress) a material by 1 m. Its unit is N/m.

Answer 38

The spring constant is the gradient of the straight part of a force-extension graph when force is on the y-axis and extension on the x-axis.

Answer 39

Force = spring constant × extension F = ke Force (Newtons, N), Spring constant (Newtons per metre, N/m), Extension (metres, m)

Answer 40

The extension of a material is directly proportional to the force applied up to the limit of proportionality (elastic limit)

Answer 41

The limit of proportionality on this graph is where the line stops being straight. It is the point at which it begins to curve. https://docs.google.com/presentation/d/1vbag61ToxKRRBOC36iATvGHtqVQD1EpBQ_w804h-D54/edit?slide=id.p#slide=id.p

Answer 42

An object which is stretched (or compressed) will return to its original length when the force is removed if it hasn’t passed the limit of proportionality.

Answer 43

An object which is stretched (or compressed) will not return to its original length when the force is removed if it has passed the limit of proportionality. There will be permanent deformation.

Answer 44

Set up a clamp stand with a spring. Clamp a ruler making sure it is vertical with a set square. Make sure the zero of the ruler is at the bottom of the spring. Add masses and record the extension of the ruler each time. Make sure to measure the extension at eye-level. https://docs.google.com/presentation/d/1wEQbENXsOcWvLOiyzDu1mG9dbHXqkeXcvpFMGVO46mA/edit?slide=id.p#slide=id.p

Answer 45

Density =mass/volume ρ = m/v Density (kilograms per metre3, kg/m3), Mass (kilograms, kg), Volume (metres3, m3)

Answer 46

The volume of a regular cuboid shaped object can be found by multiplying the width, length, and height together. Each dimension can be found accurately by repeating the measurement with a ruler in different places along each side (and then averaging) and ensuring the ruler is at 900 to the edge.

Answer 47

Add a specific amount of water into a measuring cylinder. Add the irregular object to the water and measure the new combined volume of the water and object. Subtract the volume of the water to get the volume of the object. or Fill a Eureka can to the spout with water. Add your irregular object to the water and allow the water to run into a measuring cylinder. The volume of the water displaced is the volume of the object. https://docs.google.com/presentation/d/1cuIFPrI1_0TPACrZXpAji-8O3hSeAvyJrmm3hoYYQO8/edit?slide=id.p#slide=id.p

Answer 48

Place a digital balance on a flat surface and zero it (press the tare button) before placing the object on it.

Answer 49

Uncertainty is the range of values in which we expect the true value of a measurement to lie.

Answer 50

When measurements are repeated the uncertainty in the measurement is 1⁄2 of the range. The range can be found by taking the minimum value from the maximum

Answer 51

https://docs.google.com/presentation/d/13aJZlvDzzjhW7BbPQXUjXmXJBTF5T2n3ksJab61m2h4/edit?slide=id.p#slide=id.p

Answer 52

If we consider the same volume of a substance in its solid, liquid and gaseous forms then there will be much more space between the particles in a gas than in a liquid or solid. This means that if we had the same volume we would have much less mass of gas. Since density = mass/volume then it follows that the density of a gas is less (since mass is less for an equal volume) than a solid or liquid.

Answer 53

When a substance changes state the same mass of substance will now occupy a different volume. Since density = mass/volume it follows that density will change since volume changes.

Answer 54

The resolution of a measuring instrument is the smallest change that can be read from that instrument e.g. 1 mm on a ruler, or 1° on a protractor.

PHYSICS EOY Flashcards

(78 cards)