This question asks which of Newton's laws of motion explains the necessity of wearing a seatbelt in a moving car. We need to recall each of Newton's laws and apply them to the scenario of a car suddenly stopping or changing speed.
Correct Option: A) Newton's First Law
Newton's First Law states that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. When a car suddenly stops, the passengers, due to their inertia, tend to continue moving forward. The seatbelt provides the necessary external force to counteract this inertia and bring the passenger to a stop safely.
This question tests understanding of Newton's Third Law of Motion and the concept of forces in a collision. When objects collide, they exert forces on each other. The object that causes a moving object to stop must exert a force in the opposite direction of its motion.
Correct Option: A) The wall. When the car crashes into the wall, the wall exerts a large, opposing force on the car, causing it to decelerate rapidly and stop. This is a direct application of Newton's Third Law of Motion.
This question tests understanding of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. When an astronaut throws a hammer, the action is the force exerted on the hammer. The reaction is the force exerted by the hammer back on the astronaut.
Correct Option: A) The astronaut moves in the opposite direction of the hammer's motion. This is a direct application of Newton's Third Law of Motion, where the reaction force from the hammer pushes the astronaut in the opposite direction.
This question tests understanding of Newton's First and Second Laws of Motion. The key phrase is "constant velocity," which implies zero acceleration. We need to relate this to the net force acting on the object.
A) There is no force acting on the puck. This statement aligns with Newton's First Law (Law of Inertia) and Second Law. An object in motion with constant velocity will continue in that state unless acted upon by a net external force. If velocity is constant, the net force is zero. While there might be gravitational force and normal force, they are balanced, and friction is assumed to be negligible on ice, leading to a net external force of zero in the direction of motion.
Newton's third law of motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on a second object, the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object. We need to identify the option that best illustrates this principle.
D) A balloon being inflated and released, flying around the room — When air rushes out of the balloon (action), the balloon is propelled in the opposite direction (reaction). This perfectly illustrates Newton's third law: for every action, there is an equal and opposite reaction.
The question describes a fundamental principle relating force, mass, and acceleration. We need to identify which of Newton's laws of motion precisely defines this relationship.
B) Newton's Second Law is correctly described by the statement. This law provides the quantitative definition of force and explains how forces cause objects to accelerate.