Science Exam: Unit 5 (Part One)

Explain why an object in orbit needs centripetal force acting on it. In what direction does a centripetal force act?

An object in orbit needs centripetal force so that there is an unbalanced force acting against the movement of the object. This unbalanced force that makes things move in an elliptical path (oval motion) is called a centripetal force. Centripetal means "toward the center", and gravity provides this force in orbit.

Explain why your weight but not your mass would change if you landed on Mars.

Even when the gravitational force changes, your mass will never change because mass is the amount of matter in an object, whereas weight is the measure of the amount of gravitational force on an object, so on Mars where the force changes, so would the weight, but not the mass.

How does gravity maintain the shape of the solar system?

Gravity is result of mass. All objects experience an attraction toward all other objects. This gravitational force pulls objects toward each other. Basically, gravity is holding the solar system together with its force.

Explain why Newton knew that an unbalanced force was acting on the moon and on a falling apple.

He knew that unbalanced forces are needed to change the motion of objects by changing the velocity of the objects. So he knew that an unbalanced force was causing the apple to fall. He reasoned that an unbalanced force from the moon kept the moon moving circularly around earth. So these forces were actually the same and he called it gravity.

What would happen if there were no friction between a rolling ball and the ground?

If there were no friction in between the two the ball would not be able to stop because friction is the force that opposes the motion between two surfaces that touch.

Use Newton's first law of motion to explain why air bags in cars are important during head-on collisions.

When you experience a head on collision in the front seat, your body will fall forward in motion. If you did not have air bags, your head would slam straight into he front part of the car which would be very dangerous. The air bag applies a strong unbalanced force to the motion of your body causing it to decelerate and move in an opposing direction. This keeps you safe and much healthier than you would be if you had no stronger force acting against you.

How is the acceleration of falling objects affected by gravity?

Acceleration depends on both force and mass. A heavier object experiences a greater gravitational force than a lighter object does. But a heavier object is also harder to accelerate because it has more mass. The extra mass on the heavier object exactly makes up for the additional gravitational force.

What are three ways in which the velocity of an object may change when the forces on the object are unbalanced?

Acceleration, deceleration, and change in direction.

How does the air resistance affect the acceleration of falling objects?

Air resistance is the force that opposes the motion of objects through air. The magnitude of air resistance acting on an object depends on its size, shape, and speed of the object.

A brick has a greater mass than a sponge has. Why is the acceleration due to gravity the same for both objects?

Although a brick has a greater mass, its extra gravitational force equals the acceleration out. There ends up being a balanced force from the action and the reaction of the acceleration. So, the masses are balanced out by the forces of gravitational force.

Name Newton's Three Laws of Motion. Explain and give an example of each.

Newton's First Law: -Part 1-Objects at rest will stay at rest unless there is a stronger force applied to the object -Part 2-Objects in motion will stay in motion unless a unbalanced force acts on it. Newton's Second Law of Motion: -Part 1-Acceleration and Mass; Greater mass=acceleration decreases and Less mass=acceleration increases. So, the acceleration of an object depends on the mass of the objects -Part 2-Acceleration and Force; Acceleration increases as the force on the object increases and acceleration decreases as the force applied decreases. Overall:The acceleration of an object depends on the mass of the object and the amount of force applied Newton's Third Law of Motion: -Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

What affects the magnitude of gravitational force?

The magnitude of the force depends on the masses of the objects and the distance between the objects.

Suppose that the amount of magnitude of gravity on a falling object is greater than the magnitude of air resistance on the object. What is the cumulative effect of force on the objects motion?

The object would have equal forces working against it due to the acceleration of gravity near the Earth's surface.