Sample Questions
1. I don't understand how to compute vector sums and it would be great if somebody could give me at least a formula for it, or explain the concept of vectors clearly for me.
Explain what is meant by random errors and systematic errors in experimental results.
The diagram (click here to see the diagram) shows a section of a metre rule, which is used to measure the length of the object labelled P. Which one of the following best expresses the length of object P in centimetres?
The power P dissipated in a resistor of resistance R in which there is a current I is given by
The length of the sides of a rectangle place are measured, and following measurements were made: length = 50 ± 1 mm and the width = 25 ± 1 mm.
Astronauts wish to determine the gravitational accleration on Planet X by dropping stones from an overhanging cliff. Using a steel tape measure they measure the height of the cliff as
(a) Explain why the timing readings vary by more than a tenth of a second, although the stopwatch gives readings to one hundredth of a second. ( 1 mark)
A 3.30 B 3.3 C 3.30 ± 0.05 D 3.3 ± 0.1
A ±6% B ±9% C ±16% D ±19%
Which of the following is the best estimate of the percentage uncertainly in the calculated area of the plate?
A ±2% B ±4% C ±6% D ±8%
s = 7.64 ± 0.01 m. They then drop three similar stones from the cliff, timing each fall using a hand-held electronic stopwatch which displays readings to one-hundredth of a second. The recorded times for three drops are 2.46 s, 2.31 s and 2.40 s.
(b) Obtain the average time t to fall, and write it in the form (value ± uncertainty), to the appropriate number of significant digits. (1 mark)
(c) The astronauts then determine the gravitational acceleration ag on the planet using the formula ag = 2s/t2. Calculate ag from the values of s and t, and determine the uncertainly in the calculated value. Express the result in the form ag = (value ± uncertainly), to the appropriate number of significant digits. (3 marks)
