Phys Midterm 2001

a.

A ball is thrown straight up. At the top of its trajectory, its a. velocity is zero, acc is non-zero b. velocity is non-zero, acc is zero c. velocity is non-zero, acc is non-zero

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. -Accelerating downward, stationary, accelerating upward -Stationary, accelerating downward, accelerating upward -Accelerating upward, stationary, accelerating downward -Stationary, accelerating upward, accelerating downward

c.

A car is traveling in uniform circular motion on a section of flat roadway whose radius is r. 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/4 b. rr c. 4r4r d. r/2r/2

d.

A kinematics problem asks for the value of the acceleration and provides values for x, t, and the initial velocity. Which equation should you use? a. v=v0+a⁢t b. v2=v02+2a⁢x c. x=12(v0+v)t d. x=Vot+1/2at^2

a.

A pushing force of 10 000 N is applied to the backside of a car at an angle of 25.0° above the horizontal, moving the car through a horizontal distance of 15.0 m. What is the work done by the force? a. 1.36 × 105 J b. -1.36 × 105 J c. 1.64 × 105 J

the velocity is zero and acc is -g

A rock is thrown vertically. What is true when the rock reaches its maximum height?

c.

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 remain constant. b. The speed of the station floor should decrease by a factor of 4. c. The speed of the station floor should increase by a factor of 2. d. The speed of the station floor should decrease by a factor of 2. e. The speed of the station floor should increase by a factor of 4.

b.

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 speeds of the two satellites are equal. b. The speed of the second satellite is less than the speed of the first satellite. c. The speed of the second satellite is greater than the speed of the first satellite.

b.

A square with edge length L is made larger and larger. As the square grows, the ratio of (length of the perimeter)/(area) a. increases b. decreases c. stays the same

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? -The floor provides a normal force parallel to the floor on each leg with a magnitude of 100 N. -The floor provides a force vertically upward (perpendicular to the floor) on each leg with a magnitude of 400 N. -The floor provides a force parallel to the floor on each leg with a magnitude of 400 N. -The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N.

a.

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 never in equilibrium as it falls. b. The stone is in equilibrium during the first half of its fall and then nonequilibrium for the second half. c. The stone is in equilibrium continuously as it falls.

b.

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. The string is equally likely to break for any position of the stone. b. When the stone is at the very bottom of the circle. c. When the string is horizontal. d. When the stone is at the very top of the circle.

pieR and 2R

An ant crawling along the floor follows a semi-circular path, going half way around the circumference of a circle of radius R. The distance traveled, and the displacement of the ant, are respectively:

b.

An elevator is going up at a constant speed. Near the top floor, it starts to slow to a stop. During the period that it is slowing down, its acceleration is:` a. upward b. downward c. niether

Newton's 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.

b.

Can two nonzero perpendicular vectors be added together so their sum is equal to zero? a. yes b. no c. depends

b.

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 speeds of the two cars must be the same. b. The speed of the car on the earth must be greater than the speed of the car on the moon. c. The speed of the car on the moon must be greater than the speed of the car on the earth.

a.

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. The person at the North Pole. c .Both experience the same centripetal acceleration.

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? -It is the gravitational attraction (the gravitational force) between the atoms. -It is the nuclear strong force between the nucleons in the nuclei of the atoms. -The electroweak force because the bonding in materials is carried out by electrons (electric charges).

5.92x10^-3

Express 0.00592 in scientific notation

Newton's Third Law

For every action there is an equal and opposite reaction

Newton's Second Law

Force equals mass times acceleration (F=ma)

12,500

How many meters are there in 12.5 kilometers?

9.8 m/s^2

If you drop an object in the absence of air resistance, it accelerates downward at 9.8 m/s^2. If instead you throw it downward, its downward acceleration after release is

kilograms

In the International System of Units, mass is measured using which of the following units?

a.

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.

Of the four kinematic equations, is it possible to get two possible solutions from the same equation? If so, which ones? a. No. One equation can never give two solutions. b. Yes. Whenever one of the variables is squared, that equation may provide two possible solutions. There are two such equations: x=v0t+12a⁢t2 and v2=v02+2a⁢x c. Yes. They all can give two solutions. d. Yes. Only v=v0+a⁢t.

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 μs=1.4μk for a crate in contact with a cement floor. Which of the following statements is true? -The magnitude of the static friction force on the crate is always 1.4 times as large as the kinetic friction force. -The magnitude of the kinetic friction force on the crate is always 1.4 times as large as the static friction force. -The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force.

average speeds are the same, velocities are not

Suppose you drive 1500 m due east in 2 minutes. You then turn due north and drive the same distance in the same time. Which of the following is true concerning the average speeds and average velocities for each segment of your trip?

d.

The force that opposes the motion of a moving object relative to a surface a. gravitational force b.normal force c. static frictional force d. kinetic frictional force

c.

The force that opposes the tendency of motion of a stationary object relative to a surface a. gravitational force b.normal force c. static frictional force d. kinetic frictional force

a.

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

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? -Equally spaced on a straight line. -On the corners of an equilateral triangle. -On three of the four corners of a square. -On the corners of a right triangle.

c.

To answer this question, first click here to view the associated video.A cable applies a vertical force to a crate with a mass of 70.0 kg. It first lifts the crate to a height of 12.0 m above the floor, and then lowers it back to the floor. What is the total work done by the force? a. 16500 J b. 8230 J c. Zero

True

True or False: If the magnitudes of both the x- and y-component of a vector are doubled, then the magnitude of the vector is also doubled.

False

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

c.

Two balls begin at rest at the same height (but not at the same place). At time t=0, one of them (A) is simply released, and the other one (B) is launched straight horizontally. (After t=0, both of them are then freely falling.) a. A first b. B first c. same time

a.

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? a. Car B b. Car A c. Cannot be determined from the given information.

c.

Vectors A→, B→ and C→ satisfy the following equation A→+B→=C→, and their magnitudes are related by the scalar equation A+B=C. How is vector A→ oriented with respect to vector B→? a. opposite b. parallel c. same

e.

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.

e.

Which of the following is not a system of units used in measurements? a. SI (System International) b. CGS (Centimeter, Gram, Second) c. BE (British Engineering) e. ATT (Angles, Temperature, Time) d. None of these is a system of units.

displacement will be less than or equal to distance

Which of the following is true concerning the relationship between the total distance an object moves and the displacement of the object?

a.

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. a. I only b. I and II c. I and III d. All of the above.

c.

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. a. Neither I nor II b. II only c. Both I and II d. I only

e.

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.

No force

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

a.

You and a friend are standing on the edge of a cliff of height h. You throw a ball straight upward at the same time your friend throws a ball straight downward, off the edge. You both throw with the same initial speed, v0. Assuming the ball projected upward misses the edge of the cliff on the way down, which ball will hit the ground first, and which one will hit with the greater velocity? a. ball thrown downward will hit first, both will have same velocity b. ball thrown upward will hit first, both have same velocity c. ball thrown downward will hit first, different velocity

b.

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 normal, just as if you were sitting at rest at your desk. b. You feel heavier. c. You feel lighter.

b.

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 equal to your true weight. b. Your apparent weight is less than your true weight. c. Your apparent weight is greater than your true weight.

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? -Your apparent weight is greater than your true weight. -Your apparent weight is less than your true weight. -Your apparent weight is equal to your true weight.

a.

an attractive force that acts between any two masses a. gravitational force b.normal force c. static frictional force d. kinetic frictional force

b.

the force perpendicular to a surface that prevents an object from falling through the surface a. gravitational force b.normal force c. static frictional force d. kinetic frictional force