Physics 2

Question 1

What is a force and what is energy

Answer 1

Force is a push or pull on an object which is a vector (Magnitude [represented by arrow length] and direction). Energy is the capacity to exert a force

Question 2

4 Contact forces vs 3 non contact forces

Answer 2

1 Air resistance 2 Friction 3 Normal contact 4 Tension
1 Gravitational 2 Magnetic 3 Electrostatic

Question 3

How does elasticity work and when will an object lose elasticity

Answer 3

Energy is transferred to an object and stored as elastic potential energy. When released the spring will convert this to kinetic energy
If an object is stretched past its elastic limit then it will become inelastically deformed.

Question 4

What is a Moment

Answer 4

Rotation or turning effect of a force. The further the perpendicular distance from the pivot, the larger the moment will be.

Question 5

What is Pressure

Answer 5

The amount of force per unit of area. The pressure in fluids causes a force normal (perpendicular) to any surface

Question 6

How is an object affected by pressure in a liquid

Answer 6

Pressure increases with the depth of the object because at a lower depth there is a larger weight of liquid molecules acting upon the object.

Question 7

What is upthrust

Answer 7

The upward force on an object exerted by a fluid. If an object is less dense than the liquid it will float but if not it will sink

Question 8

What 4 components is the Atmosphere made up of. Where is atmospheric pressure highest

Answer 8

Made up of Nitrogen, Oxygen, Greenhouse gases and Ozone layer (keeping out harmful radiation). Atmospheric pressure is highest at earth’s surface due to density of these gases. Hence at high altitude there is limited oxygen

Question 9

How do you find the gradient at a point on a curved graph. How do you find the distance travelled on velocity time graph

Answer 9

If a line is curved then draw a tangent on a point of a graph to find the gradient.
To find distance travelled on velocity time graph find area below line

Question 10

How is a skydiver affected by velocity and air resistance

Answer 10

Skydiver accelerates downwards resulting in increasing velocity
Air resistance increases due to factors affecting it including velocity and surface area of object
Air resistance lowers rate of acceleration downwards until eventually the acceleration stops and the skydiver falls at a constant velocity

Question 11

What are Newtons laws 3

Answer 11

1- Resultant force required to change motion of object
2- Object will accelerate if non-zero resultant force acts on it
3- When 2 objects interact forces exerted on each other are equal and opposite (Normal contact force)

Question 12

What is the Conservation of momentum. What happens to inelastic objects after a collision

Answer 12

In closed system, momentum after event = momentum before
eg Car (2000kg m/s) collides with Dinosaur (-1000kg m/s) resulting in 1000kg m/s (and inelastic objects move together acting as one particle so velocity can be calculated using combined mass)

Question 13

How is damage to people in a car crash minimised (momentum)

Answer 13

Force=Momentum/Time so to reduce impact in car crashes the momentum is spread across a longer time period using seatbelts, airbags and crumple zones

Question 14

Define:
Waves
Displacement
Amplitude
Wavelength
Time period
Frequency

Answer 14

Transfer energy from one place to another by oscillation. Displacement of wave is how far from equilibrium the wave has oscillated.
Amplitude is maximum displacement point.
Wavelength is distance between equivalent points on 2 waves.
Time period is time taken for one oscillation
Frequency is number of waves passing a point in a second Hz

Question 15

What are transverse and longitudinal waves

Answer 15

Transverse: Waves oscillate perpendicular to direction of transfer so up and down like electromagnetic waves and ripples
Longitudinal: Oscillations are parallel to direction of energy transfer like sound waves. eg some waves are more compressed than others

PS Longitudinal and parallel have 2 or more ‘L’s
Transverse has an S in it for S wave

Question 16

Describe the Reflection (ray diagrams) of light

Answer 16

Light hits boundary (mirror) at point of incidence. Angle of incidence is angle at which it hits the boundary. To find angle of reflection draw a normal perpendicular to surface.
Rays can also be transmitted (normally refracted) or absorbed (gaining energy)

Question 17

Describe Ripple tank RP

Answer 17

Ripple tank is shallow tray of water with vibrating bar connected to power pack creating waves across water surface. Above the tank is lamp and below is white paper which waves projected onto. Ruler placed by paper
Waves recorded using phone and amount of oscillations on paper is measured and divided by length of oscillations combined to find wavelength
Frequency is measured using timer next to paper and counting waves in one second
Calculate wave speed

Question 18

Why does Refraction happen

Answer 18

When waves enter a dense medium they bend towards the normal because their speed decreases and then when they exit the dense medium they bend away from the normal in their previous direction.

Question 19

Describe Reflection and refraction practical

Answer 19

Draw straight line down A3 paper using ruler
Use protractor to draw perpendicular which is the normal
Place glass block so that normal is near center of the block
Use ray box to direct light waves at block at the normal
You can see a reflected ray but also a transmitted ray which has been refracted on the other side of the block
Mark paths of each ray using crosses
Switch lights back on, remove glass block, turn off ray box and draw lines in to measure the angles of each ray.
Repeat with Perspex instead of glass to find angle of refraction is the only angle which changed

Question 20

What are the Electromagnetic waves and which side of the spectrum has the highest frequency or the highest wavelength

Answer 20

Rich (radio) Men (micro) In (infrared) Vegas (visible) Use (ultraviolet) Xray Goggles (gamma).
This mnemonic is ordered in ascending order of frequency and descending order of wavelength

Question 21

How are Radio waves used

Answer 21

Radio waves can be generated using electricity in the form of an alternating current because it has oscillating charges.
When radio waves are absorbed by a receiver they could create an alternating current with the same frequency

Question 22

Effects of Gamma, Xray + Ultraviolet waves

Answer 22

Gamma and Xray waves are ionising radiation that can cause cancer.
Ultraviolet can cause skin to age faster and skin cancer

Question 23

Uses of: Radio, Micro, Infrared, Visible, Ultraviolet, Xray + Gamma waves

Answer 23

Radio-Radio, TV
Micro-Cooking satellite communication
Infrared-Cooking, Cameras, Heaters
Visible-Fibre optic communication
Ultraviolet-Sun tanning, Energy efficient lamps
Xray+Gamma- Medical scanning

Question 24

Describe Infrared practical

Answer 24

Fill LESLIE CUBE with boiling water
Use a thermometer at a fixed distance measured by a ruler to find temperatures of different sides on Leslie cubes which are different materials or colours eg Black, White, Shiny
Dark, unreflective sides will absorb the most infrared radiation hence emit the most

Question 25

What are the 2 lenses and what do they do STUDY

Answer 25

CONVEX lenses refract parallel light rays INWARDS onto a PRINCIPLE FOCUS but CONCAVE refract parallel light rays OUTWARD. The principle of focus in a concave lens is found by connecting all the refracted rays to one point as they form a triangular shape. Distance between lens and principle focus is called focal length.

Question 26

What is Intensity and how does it affect an object. What objects are the most affected

Answer 26

The measure of the power of radiation per unit of area. The higher the intensity the hotter the object. Black body objects have the largest capability to absorb radiation hence they also can emit the largest amounts.

Question 27

What are Sound waves and what frequency do they work across

Answer 27

Longitudinal waves which travel by causing particles to collide with neighbouring particles although the conversion of sound waves to vibrations only works across certain frequencies between 20Hz - 20kHz

Question 28

What are Ultrasound waves and what frequency do they work across. What are their 2 uses

Answer 28

Waves above 20kHz which are partially reflected as they pass through boundaries allowing for reflected rays to be used in medical (babies) and industrial (submarine scanning distance from floor) imaging

Question 29

What unit is magnetic field strength measured in. What direction do magnetic fields go in

Answer 29

Magnetic field strength measured in Tesla (T). Magnetic fields go from north to south

Question 30

How is Electromagnetism created and how to find current or magnetic field direction using one another

Answer 30

Current from wire produces a magnetic field around the wire in the form of CONCENTRIC CIRCLES(more closer to wire). Direction of magnetic field is found using right hand rule ( thumb up in current's direction and curl fingers in direction of magnetic field.

Question 31

What happens to the Electromagnetic field in a circular coil, what is a Solenoid and what does it act like

Answer 31

In a circular coil of wire the magnetic fields from all sides will combine forming a single magnetic field which runs straight through the middle in a line. Adding multiple coils together forms a solenoid which acts like BAR MAGNET with a south pole and north pole.

Question 32

4 methods of Improving electromagnetic field strength in a solenoid

Answer 32

1 Increase CURRENT 2 Increase COIL NO. 3 Reduce WIRE LENGTH whilst keeping COIL NO 4 Use IRON CORE(becomes induced magnet increasing field strength and losing field when current is switched off)

Question 33

When is the Motor Effect

Answer 33

When a current/wire is placed in a magnetic field they exert a force on each other called the motor effect. Left hand rule: Stick thumb up (Force) Stick pointy finger out (Magnetic field) Stick middle finger out so it faces sideways (Current)

Question 34

In reference to the motor effect what must a wire be shaped like and connected to to form an electric motor

Answer 34

If Motor effect occurs with wire that connects back at the far end like in a coil (eg c=) then due to one end of wire experiencing an upwards force and one experiencing a downwards force then the coil will start to spin. To PREVENT coil from REVERSING its rotation every 180 degrees a SPLIT RING COMMUTATOR can be attached to both ends of the coil so that the positive and negative ends swap each turn.

Question 35

When is the generator effect caused and what 3 factors will affect the current strength

Answer 35

When wire is moved through magnetic field a PD will be induced which will induce a CURRENT if circuit is COMPLETE. Strength of current depends on: No. of coil turns Speed wire moves through field Magnetic field strength

Question 36

What are dynamos and alternators used for. What is the difference in how they are built and why.

Answer 36

Dynamos and alternators are used to generate electric current. A dynamo is built the same as an electric motor and produces direct current but alternators use slip rings which mean the direction of current swaps each half turn generating an alternating current

Question 37

How are components arranged to form Loudspeakers + Headphones

Answer 37

A coil connected to an AC supply is placed inside the magnetic field of a permanent magnet. The motor effect causes the coil to move back and forth, making the cone vibrate and produce sound.

Question 38

How are microphones designed compared to speakers

Answer 38

Same as loudspeaker but uses diaphragm instead of cone which vibrates as soundwaves hit it. This changing frequency of sound waves induces a changing pd which can be passed into an amplifier.

Question 39

How does alternating PD in primary coil induce an alternating current in the secondary coil. What is the difference between step up and step down transformers PS Alternating is abbreviated to Alt

Answer 39

Alt PD in primary coil induces Alt Current which induces Alt magnetic field in primary coil. This induces Alt magnetic field in iron core as it is an induced magnet. Alt PD is induced in secondary coil causing Alt current to flow. Step UP transformers INCREASE PD in secondary coil and DECREASE CURRENT to REDUCE ENERGY LOSS.

Question 40

4 Objects in the solar system

Answer 40

Sun (has elliptical orbit) Planets (orbited by artificial and natural satellites like moons) Comets Asteroids

Question 41

What are Galaxies

Answer 41

Large collections of star systems like the Milky Way which our solar system is a part of

Question 42

3 steps of formation of stars and why fusion is needed to make a stable star

Answer 42

1 Collections of dust gas called NEBULAS form 2 Gravity pulls dust particles together causing them to move fast so a temperature increase occurs. This gravity causes the nebula to shrink becoming dense until it turns into a hot, collapsing cloud / PROTOSTAR 3 If temperature gets high enough H nuclei join together to form He in nuclear fusion creating a star. A force of gravity acts inwards to make a star collapse but energy from fusion opposes this force causing it to expand

Question 43

What is the life cycle of a star- First 3 steps -> 2 different paths each with 3 more steps and one ends in 2 possible outcomes

Answer 43

Nebula -> Protostar -> MAIN SEQUENCE star -> RED GIANT (H nuclei run out so star begins to collapse increasing core temp so He nuclei combine into heavier elements for expansion) -> WHITE DWARF (runs out of He for fusion so shrinks/collapses in and gradually cools down) BLACK DWARF (eventually stops releasing any energy) Although instead VERY LARGE stars can turn into RED SUPER GIANTS. When they can no longer use nuclear fusion they EXPLODE producing a SUPERNOVA which creates elements heavier than iron. The REMAINS of this star can turn into a NEUTRON STAR (consists of MANY NEUTRONS) or a BLACK HOLE (LARGE GRAVITY which light can't escape)

Question 44

What happens to velocity and speed in an orbit

Answer 44

Force of gravity leads to change in velocity (speed in given direction) but not change in speed

Question 45

How are far galaxies affected by red shift and how can we detect this. What does the Big Bang theory suggest. What do 1998 observations suggest

Answer 45

Galaxies that are further away have more red shift meaning we detect light with increased wave lengths from these galaxies. Big Bang theory suggests universe began from one hot dense region which is proved by red shift because further galaxies are travelling faster. In 1998 observations of Supernovae suggested that expansion of universe is speeding up.

Question 46

S waves

Answer 46

Slow, Solids, Transverse Seisometer works out time taken to travel from one earthquake site to another Refracted by liquid outer core