Mass and weight 

Mass is the quantity of matter in a body, while weight is the Earth’s pull on a body.

Diagram of chemical balance

Source: Google

Note: lever balance and chemical balance are used to measure the mass of an object.

Note: spring balance is used for checking the weight measurement of an object.

Distinction between mass and weight

Weight is seen as a force. Force is the push or pull of an object. Weight has both magnitude and direction and is therefore a vector quantity which is measured in Newtons (N). Mass on the other hand has only magnitude and is therefore a scalar quantity which can be measured in kilograms (kg).

Past questions

1. Which of the following statements about mass and weight are correct? (Waec 2015)

1. Weight is the force of gravity on a body 
2. The mass of a body is the quantity of matter in the body 
3. The weight of a body is greatest at the equator 
4. The mass of a body is greatest at the poles

A. I and II only

B. I and III only

C. II and IV only

D. III and IV only

      Answer: A

2. An object of volume 400cm-3 and density 2.5gcm-3 is suspended from a spring balance with half its volume immersed in water. Determine the reading on the spring balance. ( Density of    water= 1gcm-3) (waec 2016)

A. 1200g

B. 1000g

C. 800g

D.400g

                 Answer: C

3.        

A bar B is balanced horizontally on two knife edges as illustrated in the diagram above. Determine the weight of the bar. (Waec 2018)

A. 10N

B. 20N

C. 40N

D. 50N

Answer: C

4. A chemical balance is used for measuring (waec 2018)

A. Volume

B. Mass 

C. Thickness

D. Density

Answer: B

5. When a brick is taken from the Earth’s surface to the moon, it’s mass (jamb 2013)

A. Remains constant

B. Reduces

C. Increases 

D. Becomes zero

Answer: A

6. Calculate the apparent weight loss of a man weighing 70kg in an elevator moving downwards with an acceleration of 1.5ms-2 (jamb 2013)

A. 686N

B. 595N

C. 581N

D. 105N

[g=10ms-2]

Answer: D

7. 

The diagram above shows plank RS pivoted at its centre of gravity O and is in equilibrium with the weights P and Q. If a weight 2P is added to P, the plank will be in equilibrium again by(jamb 2016)

A. Moving P nearer to O

B. Moving Q nearer to O

C. Adding a weight Q to Q

D. Moving P further away from O

Answer: B

8. An object of volume 1m3 and mass 2kg is totally immersed in a liquid of density 1kgm-3. Calculate its apparent weight.(jamb 2016)

A. 20N

B. 10N

C. 2N

D. 1N

[g=10ms-2]

Answer: B