Exam Technique

Question 1

In calculations, what number of significant figures should you give your answers to?

Answer 1

Always give your answer to the smallest number of significant figures used in the question

Question 2

What effect does stretching a string have on its diameter?

Answer 2

Stretching a string/stretching it more reduces its diameter and therefore its cross-sectional area

Question 3

When calculating the total current in a circuit which resistance value do you have to use?

Answer 3

You have to use the total resistance which is the resistance of the component in question plus the internal resistance

Question 4

If asked to calculate something which you don’t know which equation to use how can you work it out?

Answer 4

Look at the units of the quantity you want to work out and find which equation to use from those units

Question 5

What do forces in equilibrium on a diagram form?

Answer 5

Forces in equilibrium on a diagram form a closed loop - usually a triangle. This can be used when asked to draw an arrow showing the direction of a resultant force

Question 6

What fundamental rule given by the principle of moments do we always use when calculating moments for an object in equilbrium?

Answer 6

The principle of moments states that for an object in equilibrium the sum of clockwise moments = sum of anticlockwise moments about any point

Question 7

Define the moment of a force

Answer 7

The moment of a force about a point is force * perpendicular distance of the line of action of the force from the pivot

Question 8

When a car is decelerating what energy transfers are taking place?

Answer 8

The KE of the car is transferred to the kinetic energy of the road surface as pieces of it are pushed aside and eventually all of it is transferred to thermal energy of the road pieces as they are heated

Question 9

What equation can be used to work out voltages and resistances in a potential divider?

Answer 9

R2/R1 = V2/V1

Question 10

What quantity is not conserved in an inelastic collision?

Answer 10

Kinetic energy

Question 11

Describe the motion of two trucks immediately after undergoing an elastic collision

Answer 11

• The two trucks rebound and move in opposite directions
• The velocity of the truck with the lower mass is greater than the other one as it has the lower mass

Question 12

If a wave slows down to 3/5 of its original speed once entering a new medium what is the refractive index of that medium?

Answer 12

n = 5/3

Question 13

What must every refractive index be greater than?

Answer 13

1

Question 14

When is there no deviation in the path of a light ray when it enters an object?

Answer 14

When the ray enters the object along the normal (at right angles to the object)

Question 15

What two features must two objects have to ensure that there is no deviation of a light ray as it leaves one object and enters the other?

Answer 15

• The two objects must have the same refractive index as each other
• The two objects must be fitted to each other without gaps

Question 16

Describe the general single slit diffraction pattern that would be formed on a screen

Answer 16

1- There will be a central maximum with lower intensity maxima either side
2- The central maximum is twice as wide as the other maxima

Question 17

Whenever asked how the appearance of maxima will change in a single slit diffraction pattern what will there always be a mark for?

Answer 17

Finding the maximum order that is possible by subbing in sin90 into the equation

Question 18

How do you find the maximum number of orders possible?

Answer 18

Sub in sin90 and round down as you can’t get a fraction of an order

Question 19

How does the internal resistance and emf change from one cell to two cells in parallel?

Answer 19

The lost volts of the circuit is reduced as two cells in parallel behave as a single cell with the same emf but half the internal resistance

Question 20

Express 1A in other units

Answer 20

1A = 1 Coulomb per second

Question 21

What must be true for two sources to be coherent?

Answer 21

• The two sources have the same frequency and wavelength and have a constant phase difference between them
• The two sources are connected to the same signal generator

Question 22

If given a range of times and asked to make a calculation based on this, which value should you use?

Answer 22

The largest value in the given range

Question 23

When only is the Young’s double slit equation valid?

Answer 23

The Young’s double slit equation is only valid if the slit to screen distance is a lot greater than the slit separation

Question 24

When is the horizontal velocity of a projectile minimum?

Answer 24

Horizontal velocity is minimum when vertical velocity is zero