PHYS 201 - Final

Three masses are located in the x and y plane as follows: a mass of 6 kg is at (0 m, 0 m), a mass of 2 kg is at (3 m, 0 m), and a mass of 4 kg is at (0 m, 3 m). Where is the center of mass (or center of gravity) of the system?

(1m, 0.5m)

28. What is the kinetic energy of a thin 1.20 m uniform rod with a mass of 450 g that is rotating about its center at 3.60 rad/s?

0.350 J

30. A compound cylinder of mass 10 kg and moment of inertia of 5 kg m2 can rotate about a frictionless axle through its center O, as shown in the cross sectional view in the figure. The A rope wrapped around the outer radius R1 = 1.0 m exerts a force of magnitude F1 = 5.0 N to the right. A second rope wrapped around another section of radius R2 = 0.50 m exerts a force of magnitude F2 = 6.0 N downward. What is the magnitude of the angular acceleration of the cylinder?

0.40 rad/s2

6. What is the frequency of the wave shown in the figure?

0.5 Hz

What is 0.674/0.74 to the proper number of significant figures?

0.91

If electricity costs 7.06 cents/kWh, how much would it cost you to run a 120W stereo system 4 hours per day for 4 weeks (28 days)?

0.95 cents

16. As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?

1

A 2.0 kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m. What is the magnitude of the net force on the ball?

100 N

A car increases its forward velocity uniformly from 40 m/s to 80 m/s while traveling a distance of 200 m. What is its acceleration during this time?

12 m/s^2

A 200 N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that gravity exerts on the sled parallel to the surface of the hill?

120 N

A triatomic molecule is oriented (see figure below) as follows along the x axis: mass m is at the origin, mass 2m is at x = a, and, mass 3m is at x = 2a. What is the moment of inertia of this molecule about the y axis ?

14ma^2

A 200 N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled (the normal force)?

160 N

The sum of two vectors of fixed magnitudes has its minimum magnitude when the angle between these vectors is

180˚

Find the orbital speed of an ice cube in the rings of Saturn. The mass of Saturn is 5.68 x 1026 kg, and use an orbital radius of 1.00 x 105 km. (G = 6.67 × 10 to 11 N ∙ m2/kg2)

19.5 km/s

An ideal spring has a spring constant (force constant) of 2500 N/m. is stretched 4.0 cm. How much work is required to stretch the spring by 4.0 cm?

2.0 J

A 2.0 kg ball moving east at 3.0 m/s suddenly collides with and sticks to a 4.0 kg ball moving west at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision?

2.0 kg x m/s

A girl throws a rock horizontally, with a velocity of 10 m/s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water, assuming negligible air resistance?

20 m

The figure shows a famous roller coaster ride. You can ignore friction. If the roller coaster leaves point Q from rest, what is its speed at the top of the 25 m peak (point S)?

22 m/s

A 50 kg box is being pushed along a horizontal surface. The coefficient of static friction between the box and the ground is 0.65, and the coefficient of kinetic friction is 0.35. What horizontal force must be exerted on the box for it to accelerate at 1.2 m/s2?

230 N

A 60 kg skier starts from rest from the top of a 50 m high slope. If the work done by friction is negative 6.0 kJ, what is the speed of the skier on reaching the bottom of the slope?

28 m/s

How much kinetic energy does a 0.30 kg stone have if it is thrown at 44m/s

290J

13. Consider a pipe of length L that is open at both ends. What are the wavelengths of the three lowest pitch tones produced by this pipe?

2L, L, 2L/3

25. A child is riding a merry go round that is turning at 7.18 rpm. If the child is standing 4.65 m from the center of the merry go round, how fast is the child moving?

3.50 m/s

A 1000.0 kg car experiences a net force of 9500 Nwhile decelerating from 30.0 m/s to 15.9 m/s How far does it travel while slowing down?

34 m

The x component of vector A is 5.3 units and its y component is negative 2.3 units. The angle that vector A makes with the +x axis is closest to

340˚

1. A standing wave is oscillating at 950 Hz on a string, as shown in the figure. What is the wave speed?

380 m/s

The number 0.003010 has

4 significant figures

26. An object undergoing simple harmonic motion has a maximum displacement of 6.2 m at t = 0 s. If the frequency of oscillation is 0.255 Hz, what is the object's displacement when t =3.5 s?

4.8 m

23. A uniform, solid, cylindrical flywheel of radius 1.4 m and mass 15 kg rotates at 2.7 rad/s. What is the magnitude of the flywheel's angular momentum?

40 kg ∙ m2/s

A golf club exerts an average horizontal force of 1000 N on a 0.045 kg golf ball that is initially at rest on the tee. The club is in contact with the ball for 1.8 ms. What is the speed of the golf ball just as it leaves the club face?

40 m/s

Two vectors, of magnitudes 20 mm and 50 mm, are added together. Which one of the following is a possible value for the magnitude of the resultant?

40 mm

A man in a gym is holding an 8.0 kg weight, horizontal to the ground, at arm's length, a distance of 0.55 m from his shoulder joint. What is the torque about his shoulder joint due to the weight if his arm is horizontal?

43 N ∙ m

Vector M with arrow = 4.00 m points eastward and vector N with arrow = 3.00 m points southward. The resultant vector M with arrow + N with arrow is given by

5.00 m at an angle of 36.9º south of east

29. A solid uniform sphere of mass 120 kg and radius 1.7 m starts from rest and rolls without slipping down an inclined plane of vertical height 5.3 m. What is the angular speed of the sphere at the bottom of the inclined plane?

5.1 rad/s

12. The position of an object that is oscillating on a spring is given by the equation x = (17.4 cm) cos[(5.46 s minus 1)t]. What is the angular frequency for this motion?

5.46 rad/s

Three vectors S, T, and U, have the components shown in the table. What angle does the resultant of these three vectors make with the +x axis?

66˚ below the + x axis

24. An ice skater has a moment of inertia of 5.0 kg ∙ m2 when her arms are outstretched, and at this time she is spinning at 3.0 rev/s. If she pulls in her arms and decreases her moment of inertia to 2.0 kg ∙ m2, how fast will she be spinning?

7.5 rev/s

A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0 s. How high is the building, assuming negligible air resistance?

70 m

A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 4.0 mabove the ground. What is the mass of the box?

8.9 kg

What is the angular speed, in rad/s, of a flywheel turning at 813.0 rpm?

85.14 rad/s

If a vector has components Ax < 0, and Ay > 0, then the angle that this vector makes with the positive x axis must be in the range

90 to 180˚

27. An old LP record that is originally rotating at 33.3 rad/s is given a uniform angular acceleration of 2.15 rad/s2. Through what angle has the record turned when its angular speed reaches 72.0 rad/s?

948 rad

How much work would a child do while pulling a 12 kg wagon a distance of 4.3 m along a flat surface with a horizontal 22N force?

95J

17. Two children, Ahmed and Jacques, ride on a merry go round. Ahmed is at a greater distance from the axis of rotation than Jacques. Which of the following is a true statement?

Ahmed has a greater tangential speed than Jacques.

The magnitude of is 5.5 m, and this vector lies in the second quadrant and makes an angle of 34 ° with the +y axis. The components of are closest to:

Ax = -3.1 m, Ay = 4.6 m.

22. The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?

B

20. A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms. Which of the following statements are true about the skater during this process?

Her angular momentum remains constant.

21. When is the angular momentum of a system constant?

Only when no net external torque acts on the system.

3. Two simple pendulums, A and B, are each 3.0 m long, and the period of pendulum A is T. Pendulum A is twice as heavy as pendulum B. What is the period of pendulum B?

T

8. When a guitar is tuned to adjust it pitch, what is it that is changed?

The frequency of the fundamental.

14. When a rigid object rotates about a fixed axis, what is true about all the points in the object?

They all have the same angular acceleration.

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to

W+P sin ø

11. The total mechanical energy of a simple harmonic oscillating system is

a non-zero constant.

A ball is thrown downward in the absence of air resistance. After it has been released, which statement concerning its acceleration is correct?

acceleration is constant

Suppose that a car traveling to the west (negative x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?

acceleration is positive

Suppose that an object is moving with a constant velocity. Which statement concerning its acceleration must be correct?

accelereation is = to 0

19. If the answer to your calculation has units of kg ∙ m2/s, what type of quantity could it be?

angular momentum

The reason an astronaut in an earth satellite feels weightless is that

astronaut is falling

A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will

be directly over the package

9. A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping? (Hint: Use the Work Energy Principle)

both objects travel the same distance

10. You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.

both of you have the same amount of gravitational potential energy at the top

Two objects collide and bounce off each other. Linear momentum

definitely conserved

A 20 ton truck collides with a 1500 lb car. Which of the following statements must be true?

during the collision the force on the truck is equal to the force on the car

Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is

exactly equal to the magnitide of the change in momentum of the larger mass

Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?

exactly g

4. A simple harmonic oscillator oscillates with frequency f when its amplitude is A. If the amplitude is now doubled to 2A, what is the new frequency?

f

Jill does twice as much work as Jack does and in half the time. Jill's power output is

four times Jacks power output

A satellite encircles Mars at a distance above its surface equal to 3 times the radius of Mars. If gm is the acceleration due to gravity at the surface of Mars, what is the acceleration due to gravity at the location of the satellite?

gm/16

A 10 kg rock and a 20 kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. If the 10 kg rock reaches a maximum height h, what maximum height will the 20 kg ball reach?

h

An object moving in the +x direction experiences an acceleration of +2.0 m/s2. This means the object

is increasing its velocity by 2.0 m/s every second

A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity?

it is never beyond the pull of Earths gravity

Which of the following quantities are units of impulse?

kg x m/s

Which of the following quantities are units of momentum?

kg x m/s

The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth?

mass is the same and weight is less

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it

moves along a straight-line path in its original direction

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on the car.

neither of them does any work

A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory

neither the balls velocity nor its acceleration are zero

An object is moving with constant nonzero velocity. Which of the following statements about it must be true?

net force on the object is 0

9. A string fixed at both ends is vibrating in one of its harmonics. If we now increase only the frequency at which the string is vibrating, which of the following characteristics do we also increase?

none of the above

A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?

perpendicular to the curve inward

5. Grandfather clocks are designed so they can be adjusted by moving the weight at the bottom of the pendulum up or down. Suppose you have a grandfather clock at home that runs slow. Which of the following adjustments of the weight would make it more accurate?

raise the weight

For general projectile motion with no air resistance, the vertical component of a projectile's acceleration

remains a non-zero constant

15. A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They are all uniform and roll without slipping. In what order (first to last) do they reach the bottom?

sphere, disk, hoop

Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?

the amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greateer than that of Bob

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?

the ball

Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by this object.

the displacement is either less than or equal to the distance traveled

Which of the following statements is true about an object in two dimensional projectile motion with no air resistance?

the horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward

2. A mass on a spring undergoes SHM. When the mass is at its maximum distance from the equilibrium position, which of the following statements about it are true?

the magnitude of its acceleration is a maxiumum

18. A merry go round spins freely when Diego moves quickly to the center along a radius of the merry go round. As he does this, it is true to say that

the moment of inertia of the system decreases and the angular speed increases.

If you stood on a planet having a mass four times that of Earth's mass, and a radius two times that of Earth's radius, you would weigh

the same as you do on earth

A small car meshes with a large truck in a head on collision. Which of the following statements concerning the magnitude of the momentum change during the collision is correct?

the small car and the truck experience the same magnitude of momentum change

12. A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A: thrown straight up Case B: thrown straight downCase C: thrown out at an angle of 45ºCase D: thrown straight out horizontallyIn which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance? (Hint: Use Conservation of Mechanical Energy.)

the speed will be the same in all cases

8. You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

the work is negative on the way up and positive on the way down

You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward?

there is not a force causing you to slide forward

In an air free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles.

they hit at the same time

7. When a certain string is under tension T, the speed of a wave in the string is v. What will be the speed of a wave in the string if the tension is increased to 2T without changing the mass or length of the string?

v

11. Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?

v1=v2

10. In simple harmonic motion, when is the speed the greatest?

when the magnitude of the acceleration is a minimum

When is the average velocity of an object equal to the instantaneous velocity?

when the velocity is constant