PHYS Chapter 4&5 PLVs

False

True or False? When an astronaut is in orbit around the earth, she is weightless?

Car B

Two cars are identical except for the tread design on their tires. They both enter an unbanked horizontal curve at the same speed. Car A cannot negotiate the turn (it slides off), but Car B can. Which tread design, the one on Car A, or the one on Car B, yields the larger coefficient of static friction between the tires and the road?

Both II and III change.

A body is moved from sea level to the top of a high mountain. Which of the following statements is/are true concerning the following quantities? I. The body's mass. II. The body's weight. III. The gravitational force on the body.

(C)Accelerating downward, stationary, accelerating upward

A box is at rest on the floor of an elevator. Because of static friction, a force is required to start the box sliding across the elevator floor. Compare the size of the pushing force required to move the box, when the elevator is (a) stationary, (b) accelerating upward, and (c) accelerating downward. Rank these forces from smallest to largest. (A)Accelerating upward, stationary, accelerating downward (B)Stationary, accelerating upward, accelerating downward (C)Accelerating downward, stationary, accelerating upward (D)Stationary, accelerating downward, accelerating upward

(B)4r

A car is traveling in uniform circular motion on a section of flat roadway whose radius is . The road is slippery, and the car is just on the verge of sliding off the roadway. If the car's speed were now doubled, what would be the smallest radius of the curve it could drive on without slipping? (A)r/2 (B)4r (C)r/4 (D)r (E)2r

I and IV only

A father and his seven-year-old daughter are facing each other on ice skates. With their hands, they push off against one another. Which of the following statements is/are true? I. Each experiences an acceleration that has a different magnitude. II. Each experiences an acceleration that has the same magnitude. III. Each experiences a pushing force that has a different magnitude. IV. Each experiences a pushing force that has the same magnitude.

(A)The speed of the station floor should increase by a factor of 2.

A rotating space station creates artificial earth-like gravity. If the size of the space station is enlarged, such that its radius increases by a factor of 4, what must happen to the speed of the station floor, so that the artificial earth-like gravity is maintained? (A)The speed of the station floor should increase by a factor of 2. (B)The speed of the station floor should decrease by a factor of 2. (C)The speed of the station floor should decrease by a factor of 4. (D)The speed of the station floor should remain constant. (E)The speed of the station floor should increase by a factor of 4.

(C)The speed of the second satellite is less than the speed of the first satellite.

A satellite is in a circular orbit around a planet. A second satellite is placed in a different circular orbit that is farther away from the same planet. How do the speeds of the two satellites compare? (A)The speed of the second satellite is greater than the speed of the first satellite. (B)The speeds of the two satellites are equal. (C)The speed of the second satellite is less than the speed of the first satellite.

(B)The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N.

A square, four-legged table with a weight of 400 N rests on an even concrete floor. Assuming the weight is evenly distributed, what is the direction and magnitude of the normal force between the floor and each foot of the table? (A)The floor provides a normal force parallel to the floor on each leg with a magnitude of 100 N. (B)The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N. (C)The floor provides a force parallel to the floor on each leg with a magnitude of 400 N. (D)The floor provides a force vertically upward (perpendicular to the floor) on each leg with a magnitude of 400 N.

(B)The stone is never in equilibrium as it falls.

A stone is thrown from the top of a high cliff. Air resistance is negligible. As the stone falls, which of the following is true? (A)The stone is in equilibrium during the first half of its fall and then nonequilibrium for the second half. (B)The stone is never in equilibrium as it falls. (C)The stone is in equilibrium continuously as it falls.

(A)When the stone is at the very bottom of the circle.

A stone is tied to a string and swung along the path of a vertical circle at constant speed. When is the string most likely to break? (A)When the stone is at the very bottom of the circle. (B)When the stone is at the very top of the circle. (C)When the string is horizontal. (D)The string is equally likely to break for any position of the stone.

I and IV

An object is undergoing uniform circular motion. Which of the following changes would increase the period of the motion? I. Increase the radius of the circular motion. II. Decrease the radius of the circular motion. III. Increase the speed of the object. IV. Decrease the speed of the object.

II and III

An object is undergoing uniform circular motion. Which of the following is/are true? I. The object is moving at constant velocity. II. The object is moving at constant speed. III. The object is accelerating.

(B)The speed of the car on the earth must be greater than the speed of the car on the moon.

Consider two identical frictionless and banked curves - one is located on the earth, and the other is on the moon. If identical cars are to travel around each curve along a circle of the same radius, how must the speeds of the two cars compare? (A)The speed of the car on the moon must be greater than the speed of the car on the earth. (B)The speed of the car on the earth must be greater than the speed of the car on the moon. (C)The speeds of the two cars must be the same.

(A)The person at the equator.

Consider two people on the surface of the earth. One is on the equator, and the other is at the North Pole. Which person experiences the larger centripetal acceleration? (A)The person at the equator. (B)Both experience the same centripetal acceleration. (C)The person at the North Pole.

(A)The electroweak force because the bonding in materials is carried out by electrons (electric charges).

Considering that there are only three fundamental forces in nature from which all other forces can be derived, which of the three are responsible for the forces between atoms that hold solid materials together? (A)The electroweak force because the bonding in materials is carried out by electrons (electric charges). (B)It is the nuclear strong force between the nucleons in the nuclei of the atoms. (C)It is the gravitational attraction (the gravitational force) between the atoms.

(D)A nonzero net external force acts on the object in Case B only.

In Case A, an object is moving in a straight line at a constant speed of 9.8 m/s. In Case B, an object is moving in a straight line with a constant acceleration of 9.8 m/s2. Which of the following statements is true? (A)A nonzero net external force acts on the object in both cases. (B)A nonzero net external force acts on the object in Case A only. (C)A nonzero net external force acts on the object in neither case. (D)A nonzero net external force acts on the object in Case B only.

(D)The mass is the same everywhere.

In which location does a 15-kg bowling ball have the smallest mass? (A)On Earth. (B)On the moon where the force due to gravity is less than on earth. (C)In deep space where there is no force due to gravity. (D)The mass is the same everywhere.

(A)Three forces act on a single object. The forces all point along the same line, but may have different directions.

In which one of the following situations could an object possibly be in equilibrium? (A)Three forces act on a single object. The forces all point along the same line, but may have different directions. (B)Two perpendicular forces act on an object. (C)A single force acts on an object. (D)None of the above.

(B)The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force.

Suppose the coefficients of static and kinetic friction have values such that for a crate in contact with a cement floor. Which of the following statements is true? (A)The magnitude of the kinetic friction force on the crate is always 1.4 times as large as the static friction force. (B)The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force. (C)The magnitude of the static friction force on the crate is always 1.4 times as large as the kinetic friction force.

(B)The object can be either stationary or traveling with constant velocity.

The net external force acting on an object is zero. Which of the following statements is/are true? (A)The object can only be traveling with a constant velocity. (B)The object can be either stationary or traveling with constant velocity. (C)The object can only be stationary. (D)The object can only be traveling with a velocity that is changing.

(C)Keep one end of the rope tied to the post and have all six boys tug on the other end.

Three boys of equal strength try to break a rope (and fail) by tying one end to a fence post and tugging on the other end. Three additional boys (about the same strength as the others) come along and offer their assistance. Which of the following will maximize the tension in the rope? (A)It does not matter: the rope sustains the same tension in both cases. (B)Untie the rope from the post and have three boys tug on one end and the remaining three on the other (like a tug-of-war). (C)Keep one end of the rope tied to the post and have all six boys tug on the other end.

(B)On the corners of an equilateral triangle.

Three particles have identical masses. Each particle experiences only the gravitational forces from the other two particles. How should the particles be arranged so that each one experiences a net gravitational force of the same magnitude? (A)On three of the four corners of a square. (B)On the corners of an equilateral triangle. (C)On the corners of a right triangle. (D)Equally spaced on a straight line.

(E)All of the above.

Which of the following describe nonequilibrium conditions in the context applying Newton's laws of motion? (A)A spacecraft decelerating upon reentry into the atmosphere. (B)A car accelerating through a traffic light. (C)A ball falling off the roof of a house. (D)A roller coaster going over the crest of a hill. (E)All of the above.

(C) A car going around a circular track at a constant speed.

Which of the following does NOT represent an inertial frame of reference? (A)An airplane in straight and level flight at a constant speed. (B)A boat moving at a constant speed along a straight path. (C)A car going around a circular track at a constant speed. (D)A skydiver falling straight downward at a constant (terminal) speed.

II and IV only

Which of the following is/are true? I. Force is a scalar quantity. II. Force is a vector quantity. III. A force is a push or a pull between objects that occurs only when the objects are in physical contact. IV. Non-contact forces are also called action-at-a-distance forces.

II, III, and V only

Which of the following is/are true? I. Mass is a vector quantity. II. Mass is a scalar quantity. III. Mass is a measure of how much matter an object contains. IV. There is no relationship between force and mass. V. Isaac Newton developed three important laws of motion that describe the relationship between force and mass.

I only

Which of the following is/are true? I. The centripetal force points in toward the center of the circular motion. II. The centripetal force is independent of the object's mass. III. The centripetal force points in the opposite direction as the centripetal acceleration. IV. The centripetal force is a new and separate force created by nature, and therefore should appear in a free-body diagram.

Both I and II

Which of the following statements about centripetal acceleration is true? I. An object moving with a constant velocity cannot have a centripetal acceleration. II. An object moving with a constant speed may have a centripetal acceleration.

(E)None of the above statements are correct.

Which of the following statements is correct concerning satellites in orbit around the same planet? (A)The period of a satellite depends on its mass. (B)Satellites located closer to the planet have longer periods. (C)The period of a satellite is independent of the planet's mass. (D)If the orbital radius of a satellite doubles, then its period increases by a factor of 4. (E)None of the above statements are correct.

(C)Newton's third law is also known as the action/reaction law.

Which of the following statements is true? (A)Newton's third law is only valid for contact forces. (B)Newton's third law is also known as . (C)Newton's third law is also known as the action/reaction law. (D)Newton's third law states that for every acceleration of one object, there is an equal but opposite acceleration of another object.

(C)There is no net force acting on the jet.

Which statement is true regarding a jet moving at a constant speed of 450 m.p.h. in straight and level flight. (A)There is a net force acting on the jet, but only in the upward direction - otherwise it could not maintain flight. (B)With no net force, the jet would eventually slow down. (C)There is no net force acting on the jet. (D)With no net force, the jet would lose altitude.

(B)You feel heavier.

You and your friends are riding a rollercoaster. You enter a vertical loop-the-loop, turn upside-down, and then come out again at the bottom of the loop. This is similar to what the motorcycle stuntman did in the video. As you pass through the very bottom of the loop, do you feel heavier or lighter than normal? (A)You feel lighter. (B)You feel heavier. (C)You feel normal, just as if you were sitting at rest at your desk.

(B)Your apparent weight is less than your true weight.

You are in a car that is traveling at constant speed on a straight and level road before it suddenly starts down a hill. What can be said of your apparent weight relative to your true weight just as the car starts down the hill? (A)Your apparent weight is greater than your true weight. (B)Your apparent weight is less than your true weight. (C)Your apparent weight is equal to your true weight.

(A)Your apparent weight is less than your true weight.

You are standing on a scale and in a fast elevator that is taking you to the top of a tall building. The elevator slows as it reaches the top. What is true of your apparent weight as the elevator decelerates? (A)Your apparent weight is less than your true weight. (B)Your apparent weight is equal to your true weight. (C)Your apparent weight is greater than your true weight.