Edexcel IGCSE Physics Mathematical Skills

A student uses this apparatus to investigate how the efficiency of an electric motor varies with its input voltage.

This is the student's method.
- connect the electric motor to a d.c. power supply and a joulemeter
- attach a 1.0 kg mass to the electric motor using a length of string
- set the voltage of the power supply to 10 V and switch on the power supply
- switch off the power supply when the mass has been lifted through a distance of 50 cm
- record the input energy to the motor from the joulemeter
- calculate the energy transferred to the gravitational store of the mass
- calculate the efficiency of the motor

The student repeats this process, setting the power supply to a different voltage each time.

The diagram shows the path of a ray of light.

Measure the angle of incidence for the ray at point K.

Which of these is the angle of incidence?

A star has a circular orbit around the centre of a galaxy.

The speed of light is 3.0 x 10^8 m/s.
One light year is the distance light travels in one year.
Show that one light year is approximately 10^16 m.
[one year = 3.2 x 10^7 s]

Two students do an experiment to determine their power when running up a set of steps.

The diagram shows how they set up their experiment. Not all of the steps are shown in the diagram.

This is the students' method.
- student A stands with a stopwatch at the top of the steps
- student A starts timing on the stopwatch and shouts "go" at the same time
- student B begins to run up the steps when she hears student A shout
- student A stops timing when student B reaches the top of the steps

The students repeat their method two more times.

There are 24 steps in total and each step has a height of 19 cm .

The table shows the times recorded for student B.

Calculate the mean time from this data.
Give your answer to three significant figures.