Physics 201 MWF10:20 Fall 1998 (Ford)

Final Exam Chapts. 1--17 in Cutnell and Johnson, 4th ed.


(10 pts) 1. A block with mass 0.030 kg is resting on a horizontal frictionles surface and is attached to horizontal spring whose spring constant is 120 N/m. The block is then given a kick, that gives it an initial speed of 8.00 m/s, while the spring is initially unstretched. What is the amplitude of the resulting simple harmonic motion?

Ans.___0.126 m___


(10 pts) 2. A thin rod has a length of 0.20 m and rotates in a circle on a frictionless tabletop. The axis is perpendicular to the length of the rod at one of its ends. The rod has an angular velocity of 0.50 rad/s and a moment of inertia for this axis of 1.2 × 10^-3 kg·m². A bug (mass = 5.0 × 10^-3 kg) standing at the axis decides to crawl out to the other end of the rod. When the bug reaches the other end of the rod, what is the angular velocity of the rod?

Ans. ___0.429 rad/s____


(10 pts) 3. A small block with mass 0.2 kg is released from rest at point A that is at the top of a curved track. At point B at the bottom of the track, 5.0 m below A, the block is observed to have a velocity of magnitude 6.0 m/s. How much work was done by friction during the motion of the block from point A to point B?

Ans. ___-6.2 J___


(8 pts) 4. In a cylinder 4 moles of an ideal gas at an initial temperature of 177°C expands until its volume is doubled (V₂ = 2V₁). For the gas C_V = 12.5 J/mol·K. The gas constant is R = 8.314 J/mol·K. If the expansion is carried out at constant pressure, calculate

a) the work W done by the gas.

Ans. ___1.5 × 10⁴ J___

b) the change in internal energy U of the gas.

Ans. ___2.25 × 10⁴ J___


(12 pts) 5. 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___


(6 pts) 6. 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___

(6 pts) 7. A string 1.6 m long is tied down at both ends. A certain standing wave on the string has frequency 80 Hz and the next higher frequency standing wave has frequency 100 Hz. What is the speed of the transverse waves on the string?

Ans. ___64 m/s___


(14 pts) 8. The system in the sketch is released from rest and the 20 kg block moves downward while the other block moves up the incline. There is no friction between the block and the incline. The pulley is massless and frictionless. While the blocks are moving the tension in the rope is 90 N.

a) What is the magnitude of the acceleration of the 20 kg block?

Ans. ___5.3 m/s²___

b) What is the mass m of the block on the incline?

Ans. ___8.04 kg___


12 pts) 9. A small block with mass 0.020 kg slides without friction on the circular track shown in the sketch. The block is released from rest at point A, 14 m above the ground. Point B is at the top of a circular section of the track that has radius R = 3.0 m.

a) What is the speed of the block as it passes through point B?

Ans. ___12.5 m/s___

b) What is the magnitude of the downward normal force that the track exerts on the block as it passes through point B?

Ans. __0.849 N___


(12 pts) 10. A uniform bar weighing 120 N is attached at one end to a wall by a frictionless hinge. The bar is held in a horizontal position by a cable that makes an angle of 53° with the bar, as shown. What is

a) the tension in the cable?

Ans. ___75.1 N___

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

Ans. horizontal ___45.2 N____

   vertical___60.0 N___