Physics 201 MWF10:20 Fall 1997 (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 Carnot refrigerator takes heat from water at 0 °C and gives off heat to a room at 27 °C. Suppose that 0.200 kg of water at 0 °C is converted to ice at 0 °C by the refrigerator.

a) Q_C, the heat absorbed by the refrigerator from the water at 0 °C;

Ans. ___6.68 × 10⁴ J___

b) Q_H, the heat rejected to the room at 27 °C;

Ans. ___-7.34 × 10⁴ J___

c) W, the mechanical energy that must be supplied to the refrigerator.

Ans. ___-6.6 × 10³ J___


(12 pts) 2. A football kicked from ground level at a speed of 40 m/s and at an angle of 53° above the horizontal strikes the wall of a tall building 4.0 s after being kicked.

a) What is the horizontal distance from the point where the football was kicked to the base of the building?

Ans. ___96 m___

b) What is the maximum height above ground reached by the ball during its motion?

Ans. ___52.2 m___

c) What is the magnitude of the velocity of the ball just before it strikes the building?

Ans. ___25.1 m/s___


(11 pts) 3. A uniform bar 8 m long and weighing 120 N is attached at one end to a wall by a frictionless hinge. The bar is held at an angle of 37° above the horizontal by a horizontal cable.

a) What is the tension in the cable?

Ans. ___80 N___

b) What are the horizontal and vertical components of the force the hinge exerts on the bar?

Ans. horizontal ___80 N___

vertical ___120 N___


(6 pts) 4. A source of sound waves approaches a stationary listener at a speed of 20 m/s. The speed of sound in the air is 345 m/s. If the listener hears a frequency of 240 Hz, what is the frequency emitted by the source?

Ans. ___226 Hz___


(10 pts ) 5. A small block on a frictionless surface has a mass of 0.050 kg and is attached to a string that passes through a hole in the surface.

a) The block is originally revolving at a distance of 0.30 m from the hole with an angular velocity of 4.0 rad/s. What is the tension in the string?

Ans. ___0.24 N___

b) The string is now slowly pulled from below, shortening the radius of the circle in which the block revolves to 0.10 m. What now is the tension in the string?

Ans. ___6.48 N___


(12 pts) 6. The system sketched below is released from rest, and the hanging block of mass m is observed to move downward a distance of 6.0 m in a time of 2.0 s. The coefficient of friction between the horizontal surface and the 8.0 kg block is µ_k = 0.2. The pulley is massless and fricitionless. Calculate:

a) the acceleration of the hanging block.

Ans. ___3 m/s²___

b) the friction force acting on the 8.0 kg block while it is moving.

Ans. ___15.7 N___

c) the tension in the rope connecting the blocks while the blocks are moving.

Ans. ___39.7 N___

d) the mass m of the hanging block.

Ans.___5.84 kg___

(10 pts) 7. It is found that a force P = 20 N applied to a box keeps the box sliding along the floor at constant speed. The box weighs 50 N, and as the sketch shows, the direction of P is at 37° below the horizontal.

a) What is the magnitude of the normal force exerted on the moving box by the floor?

Ans. ___62 N___

b) What is the coefficient of kinetic friction µ_k between the box and the floor?

Ans. ___0.258___


(6 pts) 8. A cork moves up and down in a periodic way because of waves on the surface of a lake. It takes 0.5 s for the cork to travel from the highest point to its lowest. The distance between crests (peaks) of the waves on the surface of the water is 2.0 m.

a) What is the wavelength of these waves?

Ans. ___2 m___

b) What is the frequency of these waves?

Ans. ___1.0 Hz___

c) How fast are these waves traveling?

Ans. ___2 m/s___


(12 pts) 9. A block with mass 2 kg is placed on a spring that is compressed 0.5 m, so that 80 J of potential energy is stored in the spring. The spring is released, and the block travels vertically upward.



a) What is the maximum height reached by the block, measured from the initial position from which it is released?

Ans. ___4.08 m___

b) What is the speed of the block when it is 1.5 m above its initial position?

Ans. ___7.11 m/s___


(12 pts) 10. A bullet with mass m_A = 0.020 kg is fired horizontally with a speed of 200 m/s at a block with mass m_B = 1.98 kg that is initially at rest on a frictionless horizontal surface. The block is attached to a spring of force constant k = 80.0 N/m. The other end of the spring is attached to the wall. The bullet strikes the block, remains embedded inside it, and as a result of the collision the block moves to the right, compressing the spring.

a) What is the speed of the block just after the collision, when the block and bullet have come to the same speed?

Ans. ___2 m/s___

b) What is the maximum distance the spring is compressed?

Ans. ___0.316 m___