Physics 201 MWF10:20 Fall 1995 (Ford)
Final Exam Chapts. 1--23 in SZY College Physics

Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.


(9 pts) 1. A large plastic sphere is attached by a vertical rope to the bottom of a lake. The sphere has mass 60 kg and the tension in the rope is 510 N. The water in the lake has a density of 1000 kg/m³. What is the density of the sphere?

Ans. ___536 kg/m³___


(12 pts) 2. A small rock is thrown from the roof of a building. The initial velocity of the rock has a direction of 37° above the horizontal and magnitude 30 m/s. The rock strikes the ground a distance of 96 m from the base of the building.

a) What is the height of the building?

Ans. ___6.4 m___

b) What is the maximum height above the roof reached by the rock during its motion?

Ans. ___16.5 m___

c) What is the speed of the rock when it is at its maximum height?

Ans. ___24 m/s___


(14 pts) 3. Blocks A and B sit on a horizontal surface and are connected by a horizontal rope. Block B has a mass of m_B = 2 kg. The coefficient of kinetic friction between each block and the surface is µ_k = 0.4. A force F = 20 N at an angle of 37° above the horizontal is applied to block B and the blocks accelerate to the right. While the blocks are moving, the tension in the horizontal rope connecting them is T = 4.8 N.

a) While the blocks are moving, what is the magnitude of the friction force on block B?

Ans. ___3.0 N___

b) What is the acceleration of block B?

Ans. ___4.1 m/s²___

c) What is the mass m_A of block A?

Ans. ___0.60 kg___


(12 pts) 4. A block of mass 5 kg is placed on a vertical compressed spring of negligible mass. The spring is released and the block travels upward, leaving the spring behind. The initial potential energy of the compressed spring was 41 J. When the block is 0.30 m above its initial position, what is its speed?

Ans. ___3.24 m/s___


(12 pts) 5. A uniform bar that has length 8.0 m is attached by a frictionless hinge at its lower end to a vertical wall. The bar is held at an angle of 37° from the vertical by a horizontal cable. An object with mass 20 kg is suspended from the end of the bar by a vertical rope. The tension in the horizontal cable is 340 N.

a) For an axis at the hinge, what is the torque due to the tension in the horizontal cable?

Ans. ___2176 N·m___

b) For an axis at the hinge, what is the torque due to the tension in the vertical rope?

Ans. ___-941 N·m___

c) What is the weight of the bar?

Ans. ___515 N___


(13 pts) 6. A block with mass 0.49 kg is at rest on a horizontal surface. The coefficient of kinetic friction between the block and the surface is µ_k = 0.20. A bullet of mass 0.01 kg and initial horizontal velocity v₀ is fired at the block. The bullet strikes the block and remains embedded in it. As a result of the collision the block slides a distance of 0.30 m before coming to rest.

a) What is the magnitude of the work done by the friction force on the block?

Ans. ___0.294 J___

b) What was the initial speed v₀ of the bullet?

Ans. ___54 m/s___


(12 pts) 7. A cylinder with a moveable piston contains 3.0 moles of ideal gas at an initial temperature of 520 °C. The gas has C_v = 20.8 J/mol·K. Compute the work done by the gas when its temperature is decreased to 150 °C, if the temperature decrease is carried out in each of the following ways. (In your answer you must specify whether the work done by the gas is positive or negative.)

a) isochoric (V = 0)

Ans. ___0___

b) isobaric (p = 0)

Ans. ___-9229 J_____________

c) adiabatic (Q = 0)

Ans. ___+23,088 J___


(8 pts) 8. A standing wave is produced on a string of length 0.45 m that is stretched with a tension of 120 N. The frequency of the standing wave is 150 Hz. The adjacent nodes of the standing wave are separated by 0.15 m.

a) What is the mass of the string?

Ans. ___0.0267 kg___

b) What is the frequency of the next higher frequency standing wave for this string (the tension is kept fixed)?

Ans. ___200 Hz___


(8 pts) 9. A source of sound waves emits waves with frequency 300 Hz. The source is traveling to the right with speed 60 m/s. A man is to the right of the source and is moving towards it with a speed of 20 m/s. The speed of sound in the air is 340 m/s.

a) What is the wavelength of the sound waves at points to the right of the source, at the location of the man?

Ans. ___0.933 m___

b) What is the frequency f_L of the sound waves detected by the man?

Ans. ___386 Hz___