Physics test 2

Which of the following quantities represent mass?

0.34 g 120 kg

Which of the following quantities would be acceptable representations of weight?

12.0 lbs 1600 kN 899 MN

Newtons first law

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.

Two identical satellites orbit the earth in stable orbits. One satellite orbits with a speed v at a distance r from the center of the earth. The second satellite travels at a speed that is less than v. At what distance from the center of the earth does the second satellite orbit?

At a distance greater than r.

Assuming that all cars have equal speeds, which car has the acceleration of the greatest magnitude, and which one has the acceleration of the least magnitude?

D,F

Earth's orbit around the Sun is slightly elliptical. Thus, Earth actually gets closer to the Sun during part of the year. What happens to Earth's orbital speed when it is closer to the Sun?

Earth's orbital speed is greater when it is closer to the Sun than when it is farther from the Sun.

You are driving a car at 65 mph. You are traveling north along a straight highway. What could you do to give the car a nonzero acceleration?

Either press the gas or the brake pedal or turn the steering wheel.

Newtons third law

Every action has an equal and opposite reaction.

Which planet should Punch travel to if his goal is to weigh in at 118 lb? Refer to the table of planetary masses and radii given to determine your answer.

Pentune

Which of the following changes to the earth-sun system would reduce the magnitude of the force between them to one-fourth the value found in Part A?

Reduce the mass of the earth to one-fourth its normal value. Reduce the mass of the sun to one-fourth its normal value. Reduce the mass of the earth to one-half its normal value and the mass of the sun to one-half its normal value.

Which of the following statements are true?

The Sun is located at one of the foci of the planets' elliptical orbits. The path of the planets around the Sun is elliptical in shape.

A hypothetical planet has a mass one-third of and a radius three times that of Earth. What is the acceleration due to gravity on the planet in terms of g, the acceleration due to gravity on Earth?

The acceleration due to gravity is g/27.

Let v⃗ A be the velocity of the car at point A. What can you say about the acceleration of the car at that point?

The acceleration is perpendicular to v⃗ A and directed toward the inside of the track.

Let v⃗ C be the velocity of the car at point C. What can you say about the acceleration of the car at that point?

The acceleration is perpendicular to v⃗ C and pointed toward the inside of the track.

Let v⃗ D be the velocity of the car at point D. What can you say about the acceleration of the car at that point?

The acceleration is perpendicular to v⃗ D and pointed toward the outside of the track.

Let v⃗ F be the velocity of the car at point F. What can you say about the acceleration of the car at that point?

The acceleration is zero.

Newtons second law

The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.

In general, how does the coefficient of static friction compare to the coefficient of kinetic friction for the same two materials?

The coefficient of static friction can be greater than or equal to the coefficient of kinetic friction.

What is the magnitude of the gravitational force acting on the sun due to the earth?

The earth exerts 3.53×1022N of force on the sun, exactly the same amount of force the sun exerts on the earth found in Part A.

With the sun and the earth back in their regular positions, consider a space probe with mass mp=125kg launched from the earth toward the sun. When the probe is exactly halfway between the earth and the sun along the line connecting them, what is the direction of the net gravitational force acting on the probe?

The force is toward the sun.

Which of the following statements are true?

The gravitational force between two objects is proportional to the product of the masses of the two objects. The gravitational force between two objects is inversely proportional to the square of the distance between the two objects.

Two objects attract each other gravitationally. If the distance between their centers decreases by a factor of 2, how does the gravitational force between them change?

The gravitational force increases by a factor of 4.

Two objects attract each other gravitationally. If the mass of each object doubles, how does the gravitational force between them change?

The gravitational force increases by a factor of 4.

Which of the following statements are true?

The launch speed of a satellite determines the shape of its orbit around Earth. A satellite's motion is independent of its mass.

Assume that the car at point A and the one at point E are traveling along circular paths that have the same radius. If the car at point A now moves twice as fast as the car at point E, how is the magnitude of its acceleration related to that of car E.

The magnitude of the acceleration of the car at point A is four times that of the car at point E.

A packing crate is sitting at rest on an inclined loading ramp. How does the magnitude of the force of static friction compare to the other forces acting on the crate?

The magnitude of the force of static friction is equal to the magnitude of the component of the weight of the crate parallel to the inclined ramp.

An object is hanging by a string from the ceiling of an elevator. The elevator is moving upward with a constant speed. What is the magnitude of the tension in the string?

The magnitude of the tension in the string is equal to the magnitude of the weight of the object.

An object is hanging by a string from the ceiling of an elevator. The elevator is slowing down while moving upward. What is the magnitude of the tension in the string?

The magnitude of the tension in the string is less than the magnitude of the weight of the object.

Two planets, planet A and planet B, have the same surface gravity. However, planet B has twice the radius of planet A. How does the mass of planet B compare to the mass of planet A?

The mass of planet B is four times the mass of planet A.

An object moves in a circular path at a constant speed. What is the direction of the net force acting on the object?

The net force is directed toward the center of the circular path.

A planet is discovered orbiting around a star in the galaxy Andromeda at the same distance from the star as Earth is from the Sun. If that star has four times the mass of our Sun, how does the orbital period of the planet compare to Earth's orbital period?

The planet's orbital period will be one-half Earth's orbital period.

Let R be the distance between the cylinder and the center of the turntable. Now assume that the cylinder is moved to a new location R/2 from the center of the turntable. Which of the following statements accurately describe the motion of the cylinder at the new location?

The speed of the cylinder has decreased. The magnitude of the acceleration of the cylinder has decreased.

An object moves in a circular path at a constant speed. What is the relationship between the directions of the object's velocity and acceleration vectors?

The velocity and acceleration vectors are perpendicular.

Why does a satellite in a circular orbit travel at a constant speed?

There is no component of force acting along the direction of motion of the satellite.

Now assume that a satellite of mass m is orbiting the earth at a distance r from the center of the earth with speed ve. An identical satellite is orbiting the moon at the same distance with a speed vm. How does the time Tm it takes the satellite circling the moon to make one revolution compare to the time Te it takes the satellite orbiting the earth to make one revolution?

Tm is greater than Te.

Which of the following sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder at the point indicated in the diagram?

e

If acceleration due to gravity on the earth is g, which formula gives the acceleration due to gravity on Loput?

g 5.6/1.7^2

Newtons equal

kg m/s^2

After Punch Taut travels to Pentune, what actually happens to his mass and his weight?

mass remains the same; weight decreases

An object is lifted from the surface of a spherical planet to an altitude equal to the radius of the planet. As a result, which of the following changes in the properties of the object take place?

mass remains the same; weight decreases

For the merry-go-round problem, do the magnitudes of the position, velocity, and acceleration vectors change with time?

no

A ball is lodged in a hole in the floor near the outside edge of a merry-go-round that is turning at constant speed. Which kinematic variable or variables change with time, assuming that the position is measured from an origin at the center of the merry-go-round?

the position and velocity and acceleration of the ball

You throw a ball. Air resistance on the ball is negligible. Which of the following functions change with time as the ball flies through the air?

the position and velocity of the ball

The gravitational field on the surface of the earth is stronger than that on the surface of the moon. If a rock is transported from the moon to the earth, which properties of the rock change?

weight only