Physics Exam 3

negative

1. A ball has a speed of 15 m/s. Only one external force acts on the ball. After this force acts, the speed of the ball is 7 m/s. Has the force done positive, zero, or negative work on the ball?

a. The centripetal acceleration increases to 4ac.

1. A bicycle racer is traveling at constant speed v around a circular track. The centripetal acceleration of the bicycle is ac. What happens to the centripetal acceleration of the bicycle if the speed is doubled to 2v?

P does positive work, Fn and mg do zero work, and fk does negative work.

1. A box is being moved with a velocity (v) by a force (P) (in the same direction as v) along a level horizontal floor. The normal force is Fn , the kinetic frictional force is fk , and the weight is mg. Which one of the following statements is correct?

The horizontal component, FNsinθ of the normal force.

1. A car is rounding a circular curve of radius r on a banked turn. As the drawing indicates, there are two forces acting on the car, its weight mg and the normal force FN exerted on it by the road. Which force, or force component, provides the centripetal force that keeps the car moving on the circular path?

fourth

1. A force does positive work on a particle that has a displacement pointing in the +x direction. This same force does negative work on a particle that has a displacement pointing in the +y direction. In which quadrant of the x, y coordinate system does the force lie?

a. The velocity of the motorcycle is changing.

1. A motorcycle travels at a constant speed around a circular track. Which one of the following statements about this motorcycle is true?

a. obeys Newton's second and third laws.

1. A non-conservative force

A

1. A particle moves along the circular path shown, with constant speed. Its velocity vector at two different times is shown. What is the direction of the acceleration when the particle is at point x?

is accelerating

1. A race car is driving around a circular race-track with a constant speed of 100 mph. The car

a. From 3 to 4

1. A race car travels around the track shown at constant speed. Over which portion of the track is the magnitude of the acceleration the largest?

gravitational force

1. A skier is riding a ski lift chair from the base to the top of a ski run. Which of the following forces, if any, are conservative forces acting on the skier?

a. positive when you ride up and negative when you ride down.

1. A suitcase is hanging straight down from your hand as you ride an escalator. Your hand exerts a force on the suitcase, and this force does work. This work is

35 m

1. A variable force directed in the positive x direction is exerted on an object moving at a constant speed at x = 0 in the same direction. The variable force as a function of the displacement of the object is shown in the figure. If the force is applied to the object beginning at x = 5.0 m and the force does 1600 J of work, determine the magnitude of the displacement where the force is removed (F = 0 N).

900 J

1. A variable force is applied in the positive x direction to a 15-kg object as it moves in the same direction. The graph shows the resulting acceleration of the object due to the variable force. Determine the work done on the object as it moves from x = 1 m to x = 18 m by the force.

e. a car traveling on a level road.

1. All of the following are examples of potential energy except a. a flashlight battery. b. a wound-up clock spring. c. a gallon of jet fuel. d. the raised weight of a grandfather's clock. e. a car traveling on a level road.

-75 J

1. An object is initially at rest at x = 0 m. A variable force is applied to it as the object moves in the +x direction. The graph below shows the subsequent behavior of the variable force with the position of the object. What is the work done on the object between x = 15 m and x = 30 m?

True

1. If the Force (F) is constant, then the acceleration (a) is constant.

The question isn't grammatically correct, so I had a little trouble formulating my answer. I am assuming it is asking "How DOES the gravitational potential energy of the astronaut changes during the climb?" Or "how does it differ?" maybe? That being said, since it is the same astronaut, he has the same mass in both scenarios, the same height of climb, the greatest change in gravitational potential energy would be on Earth where the gravity is stronger.

1. In a simulation on earth, an astronaut in his spacesuit climbs up a vertical ladder. On the moon, the same astronaut makes the exact same climb. how the gravitational potential energy of the astronaut changes during the climb?

a. T1=0.5 T2

1. The drawing shows identical stones that are being whirled on a tabletop at the same speed. The radius of the larger circle is twice that of the smaller circle. How is the tension T1 in the longer cord related to the tension T2 in the shorter cord?

C, A, B

1. The same force F pushes in three different ways on a box moving with a velocity v, as the drawings show. Rank the work done by the force F in ascending order (smallest first).

Kinetic Energy (KE)

1. The work (W) done on an object is equal to the change in the object's

a. F1 does more work than F2 does.

1. Two forces F1 and F2 are acting on the box shown in the drawing, causing the box to move across the floor. The two force vectors are drawn to scale. Which one of the following statements is correct?

a. mechanical energy was decreased by nonconservative forces.

1. Two objects interact with each other and with no other objects. Initially object A has a speed of 14 m/s and object B has a speed of 16 m/s. In the course of their motion, they return to their initial positions. Then A has a speed of 8 m/s and B has a speed of 7 m/s. We can conclude

a. mechanical energy was increased by nonconservative forces.

1. Two objects interact with each other and with no other objects. Initially object A has a speed of 4 𝑚/𝑠 and object B has a speed of 3 𝑚/𝑠. In the course of their motion, they return to their initial positions. Then A has a speed of 8 𝑚/𝑠 and B has a speed of 7 𝑚/𝑠. We can conclude

a. All statements are true.

1. Two particles interact by conservative forces. In addition, a conservative external force acts on each particle. They complete round trips, ending at the points where they started. Which of the following have the same values at the beginning and end of this trip? a. All statements are true. b. The speed of either particle in the two-particle system. c. The total kinetic energy of the two-particle system. d. The mechanical energy of the two-particle system. e. The potential energy of the two-particle system.

Downward when it reads 75 N and upward when it reads 120 N

A 10-kg suitcase is placed on a scale that is in an elevator. In which direction is the elevator accelerating when the scale reads 75 N and when it reads 120 N?

17.5 J

A 15.0-kg object is moving in the positive x direction as a variable force is applied to the object in the same direction. The graph shows the force versus the object's displacement. How much work does the force do on the object as it moves from x = 0 to 5.00 m?

increasing the weight of the block

A block is pulled at constant speed along a rough level surface by a rope that makes an angle θ with respect to the horizontal. The applied force along the rope is P. The force of kinetic friction between the block and the surface is f. Which one of the following actions will increase the frictional force on the block?

The object must be at rest

A certain object is in equilibrium. Which one of the following statements is not true?

greater than Before climbing tension will balance the weight only , T = mg When he start upward motion then from second law of motion , T = mg + ma

A circus performer hangs stationary from a rope. She then begins to climb upward by pulling herself up, hand over hand. When she starts climbing, is the tension in the rope less than, equal to, or greater than it is when she hangs stationary?

B, C, A

A heavy block is suspended from a ceiling using pulleys in three different ways, as shown in the drawings. Rank the tension in the rope that passes over the pulleys in ascending order (smallest first).

The elevator could be moving upward at constant speed.

A man stands on a spring scale in a moving elevator and notices that the scale reading is 20% larger than when he weighs himself in his bathroom. Which one of the following statements can not be true?

170 J

A particle is moving at constant speed in the +x-direction. Beginning at x = 0 m, the particle is subjected to a variable force which is illustrated in the graph. The variable force directed in the positive x direction does 850 J of work on the object. Determine the maximum value of the force, which occurs at x = 10 m, before the force is removed.

188N

A particle is moving at constant speed in the +x-direction. Beginning at x = 0 m, the particle is subjected to the variable force in the +x direction, which is illustrated in the graph. The variable force does 2500 J of work on the object at it moves to x = 35 m. What is the maximum value of the force?

The tension is equal to the weight of the rock.

A rock is suspended from a string and moves downward at constant speed. Which one of the following statements is true concerning the tension in the string if air resistance is ignored?

four times as great

A stone is tied to a string and whirled at constant speed in a horizontal circle. The speed is then doubled without changing the length of the string. Afterward, the magnitude of the acceleration of the stone is

twice as great

An object moves around a circle. If the radius and speed are doubled, then the magnitude of the centripetal force must be

equal

An object of mass m and another object of mass 2 m are each forced to move along a circle of radius 1.0 m at a constant speed of 1.0 m/s. The magnitudes of their accelerations are

no

Conceptual Question: A sailboat is moving at a constant velocity. Is work being done by a net external force acting on the boat?

a. by the road on the car.

If a car is to travel around a corner, then the force that causes this to happen must be

9R1

If a certain car, going with speed v1, rounds a level curve with a radius R1, it is just on the verge of skidding. If its speed is now tripled, the radius of the tightest curve on the same road that it can round without skidding is

case 1 only

In which case will the magnitude of the normal force on the block be equal to (Mg + F sin θ)?

Three forces act on the 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. In none of the situations described above could the object possibly be in equilibrium. b. A single force acts on the object. c. Two perpendicular forces act on the object. Three forces act on the object; the forces all point along the same line but may have different directions

The centripetal force is the net force acting on an orbiting object that maintains it in uniform circular motion.

The centripetal force is best explained by which of the following statements?

B, C, A

The drawings show identical blocks at rest on three different inclines, each block held in place by static friction. Rank the forces of static friction in the three cases in ascending order (smallest first).

B, A, C

The drawings show three examples of the force with which someone pushes against a vertical wall. In each case the magnitude of the pushing force is the same. Rank the normal forces that the wall applies to the pusher in ascending order (smallest first).

a. slides off to the outside of the curve.

The driver of a 1000-kg car tries to turn through a circle of radius 100 m on an unbanked curve at a speed of 10 m/s. The actual frictional force between the tires and a slippery road has a magnitude of 900 N. The car

225 J

The graph shows how the value of the frictional force F acting on a ball varies as it moves along the positive x axis from x = 10 m to x = 20 m. Estimate the work done by this force during this displacement.

d

Two objects with masses m1 and m2 are separated by a distance 2d. Mass m2 is greater than mass m1. A third object has a mass m3. All three objects are located on the same straight line. The net gravitational force acting on the third object is zero. Which one of the drawings correctly represents the locations of the objects?

Parallel to the contact surface and opposite any potential relative motion between the objects

What is the direction of the force of static friction at the surface where two objects are in contact?

The negative of the work is equal to the change in the gravitational potential energy

What is the relationship between the gravitational potential energy of an object and the work done on the object by the gravitational force?

A space probe with its engines shut down, moving through a vast empty region of outer space.

Which one of the following objects is in equilibrium?