The weight is the mass of a body multiplied by the acceleration due to gravity, and the mass is the measure of the amount of matter in a body. The SI unit of mass is the kilogram (kg), and the SI unit of weight is Newton (N). A body’s mass does not change at any time. Only in extreme cases where a massive amount of energy is provided or removed from the body. In a nuclear reaction, for example, a tiny amount of matter is turned into a massive amount of energy, reducing the mass of the substance. Weightlessness is experienced due to the absence of the feeling of weight. It happens due to the lack of contact forces acting on bodies.
Read More – Mass and Weight
Important Questions with Answers
1. What is the difference between mass and weight?
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Weight |
Mass |
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In space, if there is no gravity acting on a body, then the weight of that body becomes zero. |
Mass can never be zero. |
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To define weight, direction and magnitude are needed. So weight is a vector quantity. |
Mass has magnitude, so it is a scalar quantity. |
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Weight can vary according to location. |
Mass does not vary according to location. |
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The SI unit of weight is Newton (N) |
The SI unit of mass is kilogram (kg). |
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Weight is the measure of the force of gravity on a physical body. |
Mass is the amount of matter present in a physical body. |
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By using spring balance, weight can be measured. |
By using ordinary balance, mass can be measured. |
2. Weightlessness can be experienced due to the absence of the feeling of weight.
- True
- False
Answer – a. True
Explanation – Weightlessness is a free-fall state in which gravity is withdrawn by the inertial force developed by orbital flight or other gravity-negating conditions. It happens when no contact forces are acting on bodies. The absence of the experience of weight causes weightlessness.
3. What are the similarities between weight and mass?
- Weight and mass are independent of any physical state of a matter, such as solid, gas, liquid, or plasma.
- Weight and mass have definite units and dimensions.
- Both mass and weight are measurable quantities.
- Weight and mass depend on the amount of matter in a body.
4. The mass of an object can be zero.
- True
- False
Answer – b. False
Explanation: Mass is nothing but the measure of the amount of matter which is present in a physical body. So all objects are made up of particular matter. So from this, we can say that the mass of an object can never be zero.
5. What is the formula for weight?
Weight is the measure of the force of gravity acting on a body. In other words, the weight is the product of the mass of an object and gravity. Weight can be expressed in mathematical form as,
W = mg
Where,
g = 9.8 m/s2 (acceleration due to gravity)
W = weight of an object
m = mass of an object
6. Are the mass and the weight the same on the earth?
Mass is the amount of matter present in the physical body, and weight is the measure of the force of gravity on a physical body. From the definitions, we can say weight depends on the object’s mass and location. And mass cannot depend on the location. If any object or body is in space and no gravity acts on it, then its weight can become zero. So the mass and the weight of any object or body are not the same on earth.
7. Why does mass not change in space?
According to the definition of mass, it is the amount of matter present in an object. The mass of an object is always and everywhere the same, no matter where it is in the universe. Mass does not change in space because it does not depend on the location of an object.
8. If the volume increases, the mass of an object ___________.
- increases
- decreases
- remains constant
- none of the above
Answer – c. remains constant.
Explanation – Volume does not affect the mass of an object.
9. Do photons have mass?
Photons are small packets of light, and they do not have mass. They are massless. After performing some experiments, scientists confirmed that photons have momentum as energy, but they are massless.
10. Can mass be created?
Mass cannot be created or destroyed. In chemical reactions, the mass of reactants always equals the mass of the product formed. The mass of the body does not change at any time. Only in extreme cases where a massive amount of energy is provided or removed from the body. In a nuclear reaction, for example, a tiny amount of matter is turned into a massive amount of energy, decreasing the mass of the substance.
Practice Questions
- How do you measure the mass and weight?
- What is meant by relativistic mass?
- What is the centre of mass?
- Explain the relation between mass and weight by using examples.
- What is the value of acceleration due to gravity?
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