Observations and Measurements

As a metal ball falls through a liquid, it experiences a frictional force from the liquid that opposes the motion of the metal ball.

Plan an experiment to determine the relationship between the density of a liquid contained in a measuring cylinder and the average speed of a metal ball falling through the liquid from the surface of the liquid to the bottom of the cylinder.

The average speed of the ball is calculated using the equation:

$$\text{average speed} = \frac{\text{distance travelled}}{\text{time taken}}$$

The arrangement of the apparatus is shown in Fig. 4.1.

The apparatus available includes:

• a measuring cylinder
• a metal ball
• a selection of different liquids whose densities are known.

You are not required to do this experiment.

In your plan include:

• any other apparatus needed
• a brief description of the method, including what you will measure and how you make sure that your measurements are accurate
• the variables you will control
• a results table to record your measurements (you are not required to enter any readings in the table)
• how you will process your results to draw a conclusion.

A student uses ice cubes to investigate the time taken for different masses of ice to melt when the ice cubes are placed in water.

Plan an experiment using ice cubes to investigate how the mass of ice affects the time taken for the ice to melt.

You are not required to do this experiment.

The following apparatus is available:

• top pan balance
• supply of ice cubes
• 250 $\text{cm}^3$ beaker
• supply of cold water
• stopwatch.

You may also use other apparatus and materials that are usually available in a school laboratory.

In your plan, you should:

• explain briefly how to do the investigation
• state the key variables to keep constant
• draw a table, with column headings, to show how to display readings (you are not required to enter any readings in the table)
• explain how to use these readings to reach a conclusion.

You do not have to include a diagram of the apparatus you use but you may do so if it helps your plan.

A student investigates the time taken for ice cubes to melt when they are placed in a beaker of hot water.

Plan an experiment to investigate how the thickness of the cardboard insulation around a beaker affects the time taken for the ice cubes in the beaker to melt.

You are not required to do this experiment.

The following apparatus is available:

• 250 $\text{cm}^3$ beaker
• supply of hot water
• supply of ice cubes
• thermometer
• stopwatch
• supply of 2 $\text{mm}$ thick cardboard sheets.

In your plan you should:

• explain briefly how to carry out the investigation
• state the key variables to keep constant
• draw a table with column headings to show how to display the readings
• explain how to use your readings to reach a conclusion.

A student investigates the factors affecting the bend angle $\theta$ of a metal strip.

The student places a thin straight metal strip on two supports and attaches a mass of weight $W$ to the middle of the strip. The metal strip bends as shown in Fig. 4.1.

Plan an experiment to investigate one variable affecting the bend angle $\theta$ shown on Fig. 4.1.

You are not required to do this investigation.

In your plan, you should:

• explain briefly how to carry out the investigation, including how you will measure $\theta$
• state the variables to control
• draw a table, or tables, with column headings, to show how to display your readings (you are not required to enter any readings in the table)
• explain how to use your readings to reach a conclusion.

You may draw a diagram if you think this will help your plan.

A student investigates the average speed of a trolley moving along a horizontal bench.

The trolley is placed on a ramp and released from rest. Some of the apparatus used is shown in Fig. 4.1.

The stopping distance of the trolley is the distance moved by the trolley from the bottom of the ramp until it comes to rest.

Plan an experiment to investigate how the average speed of the trolley along the bench until it comes to rest depends upon its mass.

The average speed of the trolley can be calculated using the equation shown.

$$\text{average speed} = \frac{\text{stopping distance}}{\text{time}}$$

You are not required to do this experiment.

In your plan you should:

• explain briefly how to carry out the investigation, stating any other apparatus needed
• state the key variables to keep constant
• draw a table with column headings to show how to display the readings (you are not required to enter any readings into the table)
• explain how to use your readings to reach a conclusion.