8.7B Mastery Bell Ringer

A delivery truck suddenly stops at a traffic light, causing a package in the back to slide forward. Which of Newton’s laws best explains why the package moves forward?

• Newton’s First Law – an object in motion stays in motion unless acted on by an external force

• Newton’s Second Law – acceleration depends on force and mass

• Newton’s Third Law – every action has an equal and opposite reaction

• Newton’s Law of Universal Gravitation

A scientist is testing a new space engine that applies a constant force to a spacecraft. If the force remains steady and there is no air resistance, what will happen to the spacecraft's motion over time?

• It will accelerate continuously

• It will move at a constant speed

• It will accelerate for a short time, then stop

• It will eventually slow down due to gravity

Two skateboarders push off each other with equal force, but one moves away faster than the other. What explains the difference in acceleration?

• The skateboarder with less mass experiences a greater acceleration

• The skateboarder who pushed harder moved faster

• Both skateboarders should move at the same speed

• Newton’s First Law prevents either from accelerating

Engineers designing a high-speed roller coaster must consider Newton’s Laws when determining the forces acting on riders. Which of the following changes would require the greatest increase in force to maintain the same acceleration?

• Doubling the mass of the roller coaster cars

• Cutting the mass in half and doubling the force

• Keeping mass constant and reducing force

• Reducing acceleration while increasing mass

A spacecraft in orbit is moving at a constant velocity. The pilot briefly fires the turning thrusters, then shuts them off. What happens next?

• The spacecraft immediately stops

• The spacecraft slows down but continues moving

• The spacecraft changes direction but keeps moving indefinitely

• The spacecraft accelerates in reverse