Newton's first law of motion is also known by which name?
- A.Law of inertia
- B.Law of momentum
- C.Law of action and reaction
- D.Law of gravitation
Correct answer
Explanation
The correct answer is A, the law of inertia. The first law states that a body continues in its state of rest or of uniform motion in a straight line unless an unbalanced external force acts on it, which is exactly the property called inertia.
Option B refers to the second law, which deals with the rate of change of momentum and yields the equation force equals mass times acceleration. Option C is the third law, which says that action and reaction are equal and opposite and act on different bodies. Option D, the law of gravitation, is a separate law of Newton's, stating that every body attracts every other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. The first law also defines force, by telling us that a force is what is needed to change a state of motion.
Read the full article: Motion, Force and Newton's Laws: Formulas and Facts
Practice Questions
View allWhich of the following is a vector quantity?
- A.Distance
- B.Speed
- C.Displacement
- D.Time
Show answer
It is the shortest distance from the starting point to the finishing point together with the direction of that straight line, so it has both magnitude and direction and is therefore a vector.
Read the full explanation →The equation force equals mass multiplied by acceleration follows from which law of motion?
- A.First law
- B.Second law
- C.Third law
- D.Law of conservation of energy
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It states that the rate of change of momentum of a body is proportional to the applied force and takes place in the direction of the force.
Read the full explanation →The recoil of a gun when a bullet is fired is explained by the conservation of which quantity?
- A.Energy
- B.Linear momentum
- C.Mass
- D.Electric charge
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Before firing, the gun and the bullet are at rest, so the total momentum of the system is zero.
Read the full explanation →What is the SI unit of momentum?
- A.Newton
- B.Joule
- C.Kilogram metre per second
- D.Newton per second
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Momentum is the product of mass and velocity, so its unit is the unit of mass multiplied by the unit of velocity, that is kilogram multiplied by metre per second.
Read the full explanation →A passenger standing in a moving bus falls forward when the bus stops suddenly. This is due to
- A.Inertia of rest
- B.Inertia of motion
- C.Inertia of direction
- D.Centripetal force
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While the bus is moving, the passenger's whole body moves with it. When the brakes are applied, the feet stop along with the floor of the bus, but the upper body tends to keep moving forward at the same speed, and the passenger is thrown forward.
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