Motion and Forces

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Questions and Answers

On a distance-time graph, what does a horizontal line indicate about the object's motion?

The object is at rest.

Can non-contact forces change the speed of an object? Provide an example.

Yes, gravity is a non-contact force that can change the speed of an object. For example, when an object falls, gravity increases its speed.

Why do water bottle caps have grooves? How does this relate to force and motion?

Water bottle caps have grooves to increase friction. This makes them easier to grip and turn, allowing a person to apply enough force to open or close the bottle.

Explain why forces always occur in pairs, according to Newton's Third Law.

Newton's Third Law states that for every action, there is an equal and opposite reaction. When one object exerts a force on another, the second object exerts an equal and opposite force back on the first object. Signup and view all the answers

Why doesn't a spacecraft orbiting Earth constantly need to fire its engines to maintain its orbit?

A spacecraft in orbit is in freefall, constantly falling towards Earth but also moving forward at a speed that prevents it from hitting the surface. Gravity provides the centripetal force needed to maintain the orbit. Signup and view all the answers

A bus has a maximum speed limit of 70 km/h. What is the minimum time required for the bus to travel 0.7 km under the speed limit? Express your answer in seconds.

36 seconds Signup and view all the answers

Explain how 'average speed' and 'time taken' are related when traveling the same distance. Provide a brief example.

If two objects travel the same distance, the object that takes longer has a smaller average speed. For example, if two cars travel 100 km and one takes 1 hour while the other takes 2 hours, the car that took 2 hours has a lower average speed. Signup and view all the answers

Describe the key difference between mass and weight. Which one changes with location, and why?

Mass is a measure of the amount of matter in an object and remains constant regardless of location. Weight is the force of gravity acting on an object's mass, and it changes depending on the gravitational field strength of the location. Signup and view all the answers

Define non-uniform motion and provide a real-world example.

Non-uniform motion is motion where the velocity changes over time, meaning the object is accelerating or decelerating. An example is a car speeding up on a highway or slowing down at a red light. Signup and view all the answers

If the force of gravity exerted on the Earth by the Sun is F, what is the size and direction of the force of gravity exerted on the Sun by the Earth? Explain your reasoning.

According to Newton's Third Law, the force of gravity exerted on the Sun by the Earth is the same size as F but in the opposite direction. This is because forces occur in equal and opposite pairs. Signup and view all the answers

Identify which of the following is an action-reaction pair: A person sitting on a chair and the chair supporting the person. Explain

Weight of a man sitting on a chair and the force acting on the man by the chair is NOT an action-reaction pair. The correct answer will be the weight of the man acting on the chair, and the chair pushing back on the man. Signup and view all the answers

How does air resistance typically change as the speed of an object increases? Provide an example, such as land yacht sailing.

Air resistance increases as the speed of an object increases. For a land yacht sailing, the faster it moves, the greater the air resistance opposing its motion. Signup and view all the answers

Explain the meaning of 'micro-gravity' in the context of astronauts orbiting the Earth in a spacecraft.

Micro-gravity refers to the condition where objects or people appear to be weightless. In a spacecraft, astronauts are in constant freefall around the Earth, which creates the sensation of weightlessness, even though gravity is still acting on them. Signup and view all the answers

If all the forces acting on an object are balanced, what are the two possible states of motion for that object?

If all forces are balanced, the object will either stay at rest or move in uniform motion (constant velocity in a straight line). Signup and view all the answers

What is the purpose of a free-body diagram in physics? What types of forces are included; what types of forces are excluded?

A free-body diagram shows all the forces acting on an object, but not the forces exerted by the object. It helps visualize and analyze the forces affecting the object's motion. Signup and view all the answers

Flashcards

Horizontal line on distance-time graph

Indicates the object is not moving; it remains at the same distance from the starting point over time.

Non-contact forces change speed?

Forces that act at a distance (e.g., gravity, magnetic force) can indeed change an object's speed by causing acceleration or deceleration.