BMST - Basic Math and Science Newton's Laws of Motion Questions and Answers — Questions and Answers
Question 1: A passenger in a car feels pressed back into their seat as the car accelerates forward. This sensation is best explained by which of Newton's laws?
- Newton's Second Law (F=ma)
- Newton's Third Law (Action-Reaction)
- Newton's First Law (Inertia) (Correct answer)
- The Law of Universal Gravitation
Correct answer: Newton's First Law (Inertia)
Newton's First Law, the law of inertia, states that an object at rest will stay at rest unless acted upon by an external force. [20] The passenger's body has inertia and tends to remain in its state of rest. As the car accelerates forward, the car seat applies a forward force to the passenger, causing the sensation of being pushed back into the seat. [17]
Question 2: According to Newton's Second Law of Motion, if a constant net force is applied to two objects, one with a mass of 10 kg and the other with a mass of 20 kg, which statement is true?
- Both objects will have the same acceleration.
- The 20 kg object will accelerate twice as fast as the 10 kg object.
- The acceleration of both objects is independent of their mass.
- The 10 kg object will accelerate twice as fast as the 20 kg object. (Correct answer)
Correct answer: The 10 kg object will accelerate twice as fast as the 20 kg object.
Newton's Second Law (F=ma) shows that acceleration is inversely proportional to mass (a = F/m). [7, 23] This means for a constant force, the object with the smaller mass will experience greater acceleration. Since the 10 kg object has half the mass of the 20 kg object, it will accelerate twice as much. [9]
Question 3: A rocket propels itself forward in the vacuum of space by expelling hot gases from its engine. This is a classic example of which principle?
- The relationship between force, mass, and acceleration.
- For every action, there is an equal and opposite reaction. (Correct answer)
- An object in motion tends to stay in motion.
- The force of gravity acting on the rocket.
Correct answer: For every action, there is an equal and opposite reaction.
This is a direct application of Newton's Third Law. The rocket pushing the hot gases backward is the 'action'. The 'reaction' is the hot gases pushing the rocket forward with an equal and opposite force, which propels it through space. [6, 16]
Question 4: Which of the following objects possesses the greatest inertia?
- A large, stationary cargo truck (Correct answer)
- A baseball moving at 90 mph
- A feather floating in the air
- A bowling ball resting on a rack
Correct answer: A large, stationary cargo truck
Inertia is an object's resistance to a change in its state of motion and is directly proportional to its mass. [1, 3, 11] An object's speed or state of rest does not determine its inertia, only its mass does. Of the options provided, the large cargo truck has the most mass and therefore the greatest inertia. [19]
Question 5: If the net force acting on an object with constant mass is doubled, what is the effect on the object's acceleration?
- It is quadrupled.
- It is halved.
- It remains the same.
- It is doubled. (Correct answer)
Correct answer: It is doubled.
Newton's Second Law of Motion is expressed as F = ma. [12, 21] This formula shows that acceleration (a) is directly proportional to the net force (F) when mass (m) is constant. Therefore, if the net force is doubled, the acceleration will also double. [23]
Question 6: Which of the following scenarios is the best example of a Newton's Third Law action-reaction pair?
- A swimmer pushing water backward with their hands, and the water pushing the swimmer forward. (Correct answer)
- The force of gravity pulling a book down and the normal force of a table pushing the book up.
- A car accelerating forward and the force of air resistance pushing against it.
- The Earth pulling on the Moon and the Sun pulling on the Earth.
Correct answer: A swimmer pushing water backward with their hands, and the water pushing the swimmer forward.
A Newton's Third Law pair involves two objects exerting equal and opposite forces on each other. The swimmer pushes the water (action), and the water pushes the swimmer (reaction). [14, 16, 18] In the other examples, the forces either act on the same object (gravity and normal force on the book) or involve three different objects (Earth, Moon, Sun).
BMST - Basic Math and Science Newton's Laws of Motion Questions and Answers
A passenger in a car feels pressed back into their seat as the car accelerates forward.
This sensation is best explained by which of Newton's laws?