A Level Physics OCR A Module 2 - Foundations of physics

A Level Physics OCR A Module 2 - Foundations of physics

What is a physical quantity?

Something you can measure

What does every physical quantity have?

A numerical value and a unit

What is the base unit and symbol for length?

metre m

What is the base unit and symbol for mass?

kilogram kg

What is the base unit and symbol for time?

• Second s

What is the base unit and symbol for current?

• Ampere A

What is the base unit and symbol for temperature?

• Kelvin K

What is the base unit and symbol for amount of substance?

• Mole mol

What is the homogeneity of units?

• The units in any equation must always be equivalent in terms of SI units on both sides

What is the derived base unit, symbol and SI form for energy, work and heat?

• Joule, J, kgm^2s^-2

What is the derived base unit, symbol and SI form for resistance?

• Ohm, Ω, kgm^2s^-3A^-2

What is the derived base unit, symbol and SI form for potential difference?

• Volt, V, kgm^2s^-3A^-1

What is the derived base unit, symbol and SI form for charge?

• Coulomb, C, As

What is the derived base unit, symbol and SI form for force, weight?

• Newton, N, kgms^-2

What is the derived base unit, symbol and SI form for power?

• Watt, W, kgm^2s^-3

What is the derived base unit, symbol and SI form for pressure, stress?

• Pascal, Pa, kgm^-1s^-2

What is the derived base unit, symbol and SI form for frequency?

• Hertz, Hz, s^-1

What is the prefix for 1*10^-12?

• Pico(p)

What is the prefix for 1*10^-9?

• Nano(n)

What is the prefix for 1*10^-6?

• micro (μ)

What is the prefix for 1*10^-3?

• milli(m)

What is the prefix for 1*10^-2?

• centi(c)

What is the prefix for 1*10^-1?

• deci(d)

What is the prefix for 1*10^3?

• kilo(k)

What is the prefix for 1*10^6?

• Mega(M)

What is the prefix for 1*10^9?

• Giga(G)

What is the prefix for 1*10^12?

• Tera(T)

What is the easiest way to make estimates?

• Compare the situation with one you are more familiar with

What are random errors?

Errors that cause readings to be spread about the true value due to the results varying in an unpredictable way.

What can reduce the effect of random errors?

Using more sensitive apparatus and repeating your experiment and taking an average

What do random errors reduce?

The precision of your results

What are systematic errors?

Errors that usually cause each reading to be different to the true value by the same amount

What do systematic errors reduce?

The accuracy of your results

What should you do if you suspect a systematic error?

You should repeat the experiment with a different technique or apparatus and compare the results.

How can you calibrate your apparatus?

By measuring a known value

When you are adding or subtracting data what do you do with the uncertainties?

You add the absolute uncertainties

When you are multiplying or dividing data what do you do with the uncertainties?

You add the percentage uncertainties

When you are raising data to a power what do you do with the uncertainties?

You multiply the percentage uncertainty by the power

How do you measure the accuracy of your results by using the percentage difference?

Percentage difference = (experimental value - accepted value)*100 / accepted value

How do you use error bars?

When you are plotting a graph, you show the uncertainty in each measurement by using error bars to show the range the point is likely to lie in

What is the worst gradient?

The gradient of the line that is furthest from the line of best fit through the error bars

What is the uncertainty in the gradient?

Given by the difference between the best gradient of the line of the best fit and the worst gradient

What is a scalar quantity?

A quantity that has no direction, just magnitude

What is a vector quantity?

It has a magnitude and direction

Give some examples of scalar quantities

length/distance, Speed, Mass, Temperature, Time, Energy

Give some examples of vector quantities

Displacement, Velocity, Force, Weight, Acceleration, Momentum

What is finding the resultant vector?

Adding or subtracting two or more vectors

How do you draw a diagram of adding vectors?

You draw the vectors 'tip to tail'

What is resolving a vector?

The opposite of finding a resultant vector, you split it into the horizontal and vertical components

How do you resolve a vector for an object on a slope?

If you have an object on a slope choose your directions as along the slope and at right angles to it. Along the slope is W Sin theta

How do you resolve vectors to find the resultant vector?

Resolve into vertical and horizontal then add together