Physics Paper 6 Revision Notes

Physics revision notes….(paper6) Centre of mass experiment (with the lamina): How to minimize inaccuracy when marking the lines : you view the string directly in front of card. Centre of mass of a plane lamina (Very important for Paper 6) 1. Make a hole in the lamina. 2. Hang it so it can swing freely. 3. Hang a plumb line in the hole and mark the line it passes through. 4. Repeat the procedure again to get another line 5. Their intersection point is the centre of mass. Stability of simple objects The position of the centre of mass affects its stability. If the centre of mass of an object is low, it is less likely that will tip over if we tilt it. To increase stability we should: 1. Increase surface area 2. Making the object shorter. Why angle i is NOT equale to angle r in ray experiment: - thickness of pins -thickness of mirror -protractor is not precise In an experiment to do with the cooling of water,

there are certain things which must be kept the same: - initial temp. -thickness of test-tubes ( more heat lost when thinner etc.) -vol. of water -thickness of cotton wool -depth of the thermometer in the water -avoid droughts

Examples of insulators that you can wrap things with: -bubble wrap -fiberglass Styrofoam is a good insulator , however you cannot wrap it around things as it breaks easily. inaccuracy of ray box method: thickness of rays. inaccuracy of pin method: pins not straight, or too close, or thickness of lines drawn. Symbol for extension is 'x' or 'e'. A ruler is called a 'rule'. ALWAYS ROUND TO 3.SIG.FIGS. To improve accuracy, put pins in the light ray experiment FURTHER APART to avoid parallax error. So, I I I is better than I I I (where I is the pins) Precautions for circuit readings of I and V so that accurate: For I specifically :

-limit current so that temp. doesn't increase -use a tapping meter For I and V: Switch off between readings. θ this is the symbol for Celsius temp. (theta) T this is the symbol for Kelvin temp. In light ray experiment, lengths are in mm.

Fair test for pendelum experiments: -length of pendelum -shape of bob -no. of swings -amplitude If a statement is 'directly proportional', the justification would always be , ''straight line that goes through the origin''. If you're comparing the extensions of springs of different materials, certain things have to be the same: -the cross-section of the springs -the length of the springs -the room temperature

How to reduce the heating effect of current: -Add a variable resistor -reduce current -reduce voltage or power

-switch off between readings Precautions for focal length experiments: -do it in a darkened room -clamp ruler to bench -avoid parallax error when reading the lengths -make sure that the obejct/lense/screen are all perpendicular to bench. -and of course, repeats. A question one came up and asked to draw a diagram of a load on a ruler on a pivot. Well, this meant that the ruler was unbalanced, and so this means that when you draw it, you must show that the ruler is tilted. DON'T FORGET TO WRITE DOWN THE UNITS AFTER EACH ANSWER!!! An important precaution for spring experiments is to wait for the spring to stop moving and then record the length Why the student measures the time taken for twelve swings of the pendulum rather then just one swing?  Reduce human erros  Give more accurate value of time taken (T)  Gives an average of T

TIPS OF GRAPH WORK

Label the axes (quantity/unit) . what to label on Yaxis and on X-axis is always given in the questions. Suitable scales … Eg: in 2’s 5’s 10’s…etc NEVER USE 3’s 7’s 11’s..etc bcuz would be difficult to plot the graph.

The graph must occupy at least 2/3 grid.. better to use the whole graph grid to be on the safe side. Use a FALSE ORIGIN(meaning NOT to start the origin from 0) if required. For calculating the gradient: It must use more than ½ the line. Must use the points that are on the line. DO MEMORISE THE UNITS VERY IMPORTANT …THEY MOSTLY ASK IN THE TABLES… IN MOST PAPERS THEY ASK TO DRAW REFLECTION AND REFRACTION MAKE SURE U KNOW HOW TO DRAW THAT … BEST TIP FOR THE IS TO FOLLOW THE INSTRUCTION AND APPLY IT IN ORDER THIS WAY U WONT MESS UP.

GOOOOOOOOOOOOD LUCKKKKK!!!!!!!!!!!!!!!!!! :D DON’T FORGET TO REMEMBER ALLAH, HE IS ALWAYS THERE FOR YOU.