Pure physics

How does an object accelerate within a vacuum with gravity?

It accelerates indefinitely (infinitely)

What is the formula for force in terms of mass, radius and speed?

F = (mass x velocity²) over radius

What are scientists currently researching for producing energy on a large scale?

Nuclear fusion

How does the density of a liquid affect it’s pressure?

The denser the liquid the more pressure it puts on a mass

What increases as you go deeper below a liquid?

Pressure

What is the formula for change in pressure within a liquid?

Change in pressure = density x gravity x depth

What is the lowest temperature that particles can reach?

-273 C also known as absolute zero

Why do microscopic particles like smoke and pollen move randomly?

Because they collide with light fast-moving molecules such as air or water

Where does kelvin equal to zero Celsius?

-273 C

How do we calculate kelvin from Celsius?

We add 273

When a fixed mass of a gas is at a constant temperature, how are the pressure and volume linked to one another?

They are inversely proportionate

What happens to solids when they are heated?

They vibrate and push apart slightly however their strong intermolecular forces limit expansion

What happens to liquids when they are heated?

Particles move past one another and expand more than solids as intermolecular forces are weaker

What happens to gases when they are heated?

Particles expand significantly to maintain constant pressure as intermolecular forces are virtually non-existant

What is internal energy?

It is the total energy stored by the particles inside a system

What happens to an object’s internal energy when temperature rises?

It increases

What is temperature a measurement of in physics?

Average kinetic energy of the particles

What happens to average kinetic energy when temperature increases?

It also increases

What is specific heat capacity?

It is the amount of energy required per unit of mass for an increase by one Celsius (or kelvin)

What is the equation for specific heat capacity?

Specific heat capacity = energy transferred / (mass x temperature change)

How do you measure the specific heat capacity for a solid?

Place a immersion heater and thermometer into two pre-drilled holes in a metal block with known mass (insulate to reduce thermal energy loss), measure initial temperature and heat with heater connected to a joulemeter (to measure energy transferred), then record final temperature after heating and calculate.

How do you measure the specific heat capacity for a liquid?

Place a measured mass of liquid into an insulated beaker with an electric immersion heater and thermometer. Record the initial temperature and turn on heater for a set time and record energy transferred, before measuring final temperature (ensure temperature is evenly distributed) . Then calculate.

How does evaporating liquid cool an object?

As the liquid evaporates (endothermic), it takes energy from the surrounding liquid and object in order to break free and escape as a gas

How do we test for good and bad thermal conductors?

Have two rods of identical dimensions but different materials and attach a pin to one end of both rods with petroleum jelly (wax). Heat both sticks simultaneously with a bunsen burner and record how long it takes for the wax to melt and the pins to fall.

Why is thermal conduction bad in most liquids and gases?

Due to the particles being spaced far apart and not in a fixed lattice meaning a very low frequency of collisions, making conduction slow and inefficient

What solids that are non-metals are good conductors of thermal energy?

Dense solids such as glass, stone and ceramics as their particles are tightly packed together, but are still worse than metals as they lack delocalised electrons

How do we demonstrate convection currents?

Drop a potassium manganate(VII) crystal into cool water towards one corner, heat the surface below the crystal using a small bunsen burner flame. Bright purple steam will be seen rising from the heated point, spreading at the top, and sinking down the cooler side, creating a visible convection current.

What objects emit thermal radiation?

All objects (considering they are above absolute zero)

What wave on the electromagnetic spectrum is thermal radiation?

Infrared radiation

What happens when an object receives more thermal radiation than it gives out?

It increases in temperature

What happens when an object receives less thermal radiation than it gives out?

It decreases in temperature

What happens when an object receives equal thermal radiation as it gives out?

It stays at a constant temperature

What are two factors that affect rate of thermal radiation?

Temperature and the surface area of the object

What is an example of heating a room by convection?

Using a heater, which heats nearby air, causing it to rise and cool air to fall and become heated, creating a convection cycle

How are cooking pans structured specifically for thermal conduction?

They have large bases made of metal to absorb heat easily, while the handle is made out of plastic or wood (poor conductors) to keep our hands safe

What are the three ways that burning coal/wood transfers thermal energy?

Radiation (the coal burning and radiating heat outwards around the room), convection (hot air rises and escapes through the chimney pulling cool air in) and conduction (thermal energy conducts through the solid grate and embers touching the fuel)

What are the three ways that a radiator transfers thermal energy?

Conduction (heat from the engine conducts into the circulating liquid content, and then from the coolant into the metal fins), convection (air flows through the radiator fins heats up, expands and carries thermal energy away via forced convection) and radiation (the dark, high surface area metal fins radiate infrared energy directly into the surrounding air)

How do we show reflection using a ripple tank?

Place a flat barrier in the water path and observe the water wavefronts hit the barrier and bounce off

How do we show refraction using a ripple tank?

Submerge a flat glass plate into part of the tank to make a region shallower, observe how wave speed and wavelength decreases and frequency stays the same as the waves move from deep to shallow water

How do waves with a longer wavelength diffract at an edge?

They curve and spread significantly into the shadow region behind the barrier

How do waves with a shorter wavelength diffract at an edge?

They experience less diffraction, spreading very little as they pass the edge, leaving a distinct shadow region

How can you find the refractive index using the critical angle?

Refractive index = 1 / sin(c)

What kind of lens do you use for short-sightedness people?

A diverging lens

What kind of lens do you use for long-sightedness people?

A converging lens

How is visible light of a single frequency (one colour) described?

Monochromatic

What type of electromagnetic wave do phones and wireless internet use?

Microwaves

What type of electromagnetic wave does Bluetooth use?

Radio waves

What type of electromagnetic wave do optical fibres use?

Visible light and infrared

What is analogue signal?

A continuous variable voltage or signal that can take any value within a range (like a smooth wave)

What is digital signal?

A signal consisting of discrete pulses that only take two state: HIGH / LOW (1 and 0)

How can sounds be transmitted?

As both digital and analogue signals

What are the benefits of digital signalling?

Increased data transmission rate and accurate signal regeneration

What is the approximate speed of sound in air?

330-350 m/s

How do we measure the speed of sound in air?

Stand a measured distance away from a large flat wall, clap two wooden blocks together, measure the time it takes for the sound to return and calculate