Mass, Weight & Density (Cambridge (CIE) IGCSE Physics)

Fig. 1.1 shows a coil of wire.

A student measures the length of the coil using a ruler. His measurement is 3.8 cm.

There are 20 turns of wire in the coil. The student uses his measurement to calculate the average thickness of the wire.

(i) Show that the average thickness of the wire is about 0.2 cm.

average thickness of wire = .................................................. cm [2] 

(ii) The student’s measurement of 3.8cm is inaccurate.

 Suggest one reason why the measurement is inaccurate.

[1]

The volume of the wire in the coil is 16.6 cm³ and its mass is 148 g. 

Calculate the density of the metal used for the wire in the coil.

density = ............................................. g/cm³ 

The student has a measuring cylinder and a beaker of water, as shown in Fig. 1.2.

 Describe how the student can determine the volume of the coil by using the equipment shown in Fig. 1.2.

A 250 cm³ beaker containing some liquid is shown in Fig. 2.1.

(i) A student has a measuring cylinder and a balance.

Describe an experiment to determine the density of the liquid.

[5]

(ii) Suggest the unit of density used by the student.

[1]

Fig. 2.2 shows a block of polythene.

(i) Polythene floats in water. Explain why polythene floats.

[1]

(ii)

The weight of the polythene block is 0.84 N.

Calculate the mass of the block.

mass = ..................................................... kg [3]

A student has an irregularly shaped piece of metal, a beaker of water and a measuring cylinder, as shown in Fig. 2.1.

Describe how the student can accurately determine the volume of the piece of metal using the equipment provided.

The student measures the mass of the piece of metal. Its mass is 146 g.

(i) State the name of the instrument used to measure the mass.

[1]

(ii) The volume of the piece of metal is 20 cm³.

Calculate the density of the metal. State the unit.

density = ......................................................  [4]

Fig. 2.1 shows a raft floating on water.

A force of 20 000 N acts on the raft in the direction of the arrow shown in Fig. 2.1.

(i) State the name given to the force shown in Fig. 2.1.

[1]

(ii) Calculate the mass of the raft.

mass = ......................................................kg [3]

A sail is added to the raft, as shown in Fig. 2.2.

Fig. 2.2 shows the horizontal forces acting on the raft at one moment.

  Calculate the resultant horizontal force acting on the raft and state the direction of this force.

force = ............................................................ N

  direction = ...........................................................

Explain, in terms of their molecules, why the density of water is greater than that of oil.

State the difference between mass and weight.

The mass of a bucket is 1.2 kg.

When the bucket is filled with oil the total mass is found to be 14.1 kg.

Calculate the weight of the oil.

weight of oil =....................................................

The volume of the oil in the bucket is 0.0163 m³. 

Calculate the density of the oil.

density = ....................................................

Fig. 1.1 shows a plastic water barrel. The barrel is full of water.

The water barrel contains 0.050 m³ of pure water. The density of pure water is 1000 kg/m³.

Calculate the mass of pure water in the barrel.

mass of water = ...................................................... kg 

The density of sea water is 1030kg/m³. The density of the plastic is 1000kg/m³. Use this information and the information in (a) to state and explain whether the full barrel will float in sea water.

A student has a metal object.

(i) The student measures the mass of the object.

State the name of the equipment used to measure the mass.

[1]

(ii) The mass of the metal object is 1260 g. The volume of the metal is 150 cm³.

  Calculate the density of the metal. Include the unit. 

density = .............................................. [4]

(iii) The mass of the metal object is given in grams. State the mass in kg.

   mass = .................................................... kg [1]

A vase is placed on a table. Forces X and Y act on the vase, as shown in Fig. 1.1.   The mass of the vase is 0.25 kg. The vase is not moving.

  Calculate the value of force X and the value of force Y.

A group of students are asked to find the volume of their Physics Laboratory.

Fig. 1.1 is a top view of the room and shows the measurements of each wall.

Fig 1.1

The lab has a ceiling which is at constant height, found to be 3.5 m.

(i) State an instrument that would be suitable to make these measurements.

[1]

(ii) Describe a method the students could use to reduce errors in their measurements.

[2]

(iii) Explain how they should ensure the results are reliable.

[2]

Calculate the volume of air in the room.

The density of the air is 1.2 kg / m³. Calculate the mass of air in the room.

Describe a method the students could use to find the density of air. You do not need to include details of the calculation.

The students have been provided with the following equipment: 

Balloon
Large measuring cylinder
Bucket
Water
Digital scales

In a car boot sale a student sees what the seller says is a model soldier made from copper. The student buys the model, hoping that it is really made from gold.

At Science Club the student is allowed to investigate their theory.

Describe how the volume of the model could be measured.

You may use a diagram if you wish.

The student used a force meter for the next stage of their investigation.

(i) Describe how the force meter is used to find mass.

[3]

(ii) Explain how the student reduces errors in their reading.

[1]

The mass of the model is 625 g and the volume is 72 cm³.

The densities of various metals commonly used in model-making are:

By comparison with values in the data table, discuss the student's findings and whether the model is made from either copper or gold.

Another student decides to find the density of a table-tennis ball using the same apparatus.

Discuss a change the student have to make before making their measurements.