Physics Practical Exam P3 Flashcards
Problems from Ball bearings and craters
1- Two results are not enough to draw a valid conclusion.’
2- The ruler is too wide to measure the depth of the crater.
3-There may be a parallax error when measuring the top level of the crater.’
4- It is difficult to release the ball-bearing without giving it a sideways velocity, leading to a distorted crater.’
Solutions for the problem of ball bearings and craters
1- Take more results and plot a graph of D against d.
2- Use a knitting needle and mark the sand level on the needle and then measure with a ruler
3- Keep the eye parallel to the horizontal level of the sand, or use a stiff card.’
4- Use an electromagnet to release the ball.’
Problems for stop watch ig
1- Taking readings for just two masses was not enough.
2- ‘It was difficult to start the stopwatch at the same instant that I dropped the stone and to stop it exactly as it hit the ground. I may have been late because of my reaction time
3- My hand was not steady and so I may not have dropped the stones from exactly the same height each time.
4- ‘The times that I measured were very short not much greater than my reaction time - so reaction time had a great effect.’
Solutions for stopwatch ig
1- ‘I should use a great range of different masses and plot a graph of the average time to fall to the ground against the mass of the object.’
2- ‘Film the fall of each stone with a video camera which has a timer in the background. When the video is played back, frame by frame, I will see the time when the ball hits the ground on the timer.
3- Use iron objects which hang from an electromagnet. When the current in the electromagnet is switched off, the object falls
4- Increase the distance of fall so that the times are larger. This will make the uncertainty in each time measurement smaller in proportion to the time being measured.’
Problems in timing oscillations
1- Taking readings for just two lengths was not enough.’
2- ‘It was difficult to judge the end of the swing.
3- The oscillations died away too quickly.’
4- ‘The times were too small to measure accurately, as my reaction time was a significant fraction of the total time.’
Solutions in timing oscillations
1- Use more than two lengths and plot a graph of the average time squared against the length of the string.’
2- Use a fiducial mark at the centre of the oscillation as the position to start and stop the stopwatch.
‘Use an electronic timer placed at the centre of the oscillation to measure the time.’
‘Make a video of the oscillation with a timer in the background and play it back frame by frame.’
3- Use a heavier mass which swings longer.
4- Use longer strings.’
‘Time 20 rather than 10 oscillationsl
Newton meter provlems
1- ‘Taking readings for just two masses was not enough.’
2- ‘It was difficult to zero the newton-meter used horizontally
3- ‘The block starts to move suddenly and it is difficult to take the reading as this happens.’
4- ‘The reading of F was very low on the scale and gave a large percentage uncertainty.’
Newton metres solutions
1- ‘Use more than two masses and plot a graph of the force against the mass.’
2- Use a force sensor and computer.’
‘Use a pulley and string to connect a tray to the block. Then tip sand onto a tray until the block starts to move. The weight of the sand and tray is then the force.
3- Video the experiment and play back frame by frame to see the largest force.’
‘Use a force sensor and computer
4- ‘Use heavier masses on top of the block.
Problems for circuits
1- ‘Taking readings for just two lengths was not enough.’
2- ‘Difficult to measure the length of the wire as the clips have width and I don’t know where inside they grip the wire.’
3- ‘The scale is not sensitive enough and can only measure to 0.05 V
4- ‘The voltmeter reading fluctuates because of contact resistance.’
