1.1. An object falls off a cliff which is at a height, h, above the ground. The object takes 13.8 seconds to hit the ground.

It is estimated that there is a percentage uncertainty of ±5% in measuring this time interval. A guidebook of the local area states the height of the cliff is 940 ± 10 m.

Calculate the acceleration of free-fall of the object and its absolute uncertainty to an appropriate number of significant figures.

1.2. The only instrument used in this experiment was a stopwatch.

Suggest one possible source of systematic error and one source of random error in this investigation and explain how these errors could influence the value of acceleration of free-fall of the object determined in part (a).

1.3. The experiment is repeated in a lab and the time is measured electronically. A student performs an experiment to find the acceleration due to gravity.

The time t for a spherical object to fall freely through measured vertical distances s is measured. The results are shown in Table 1. 

Table 1

Complete the missing data in Table 1 and plot the data on Figure 1 below, including error bars and a line of best fit.

Figure 1

1.4. The uncertainty in each value of s is ± 0.002 m.

Hence, or otherwise, calculate the value of g for this experiment and its percentage uncertainty.