American University in Cairo
Department of Physics
Final Exam
Physics (111) Time: 2 Hours

Answer the following problems

1)The mass of the blue puck in Figure is equal to 1.2 the mass of the green one. Before colliding, the pucks approach each other with momenta of equal magnitude and opposite directions, and the green puck has an initial speed of 10.0 m/s. Find the speeds of the pucks after the collision if half the kinetic energy is lost during the collision.

speed of Blue puck: 5.89 m/s
Speed of Green puck: 7.069 m/s

2)The speed of a moving bullet can be determined by allowing the bullet to pass through two rotating paper disks mounted a distance d apart on the same axle as shown in Fig. From the angular displacement of the two bullet holes in the disks and the rotational speed of the disks, we can determine the speed v of the bullet. Find the bullet speed for the following data: d = 80 cm, = 900 rev/min, and = 31.0°.

The velocity of the bullet =139.35 m/s

3)A block of mass m1 = 2.00 kg and a block of mass m2 = 6.00 kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = 0.250 m and mass M = 10.0 kg. These blocks are allowed to move on a fixed block-wedge of angle = 30.0 as in Figure P10.37. The coefficient of kinetic friction is 0.360 for both blocks. Draw free-body diagrams of both blocks and of the pulley. Determine (a) the acceleration of the two blocks, and (b) the tensions in the string on both sides of the pulley.

a=0.3086 m/s2
T1=7.673 N
T2=9.216 N

4) A train is moving parallel to a highway with a constant speed of 20.0 m/s. A car is traveling in the same direction as the train with a speed of 40.0 m/s. The car horn sounds at a frequency of 510 Hz and the train whistle sounds at a frequency of 320 Hz. (a) When the car is behind the train what frequency does an occupant of the car observe for the train whistle? (b) After the car passes and is in front of the train, what frequency does a train passenger observe for the car horn?(speed of sound is 343 m/s)

a) f=338 Hz
b) f=383 Hz

5) The active element of a certain laser is made of a glass rod 30.0 cm long by 1.50 cm in diameter. If the temperature of the rod increases by 65.0°C
, what is the increase in (a) its length, (b) its diameter, and (c) its volume? Assume that the average coefficient of linear expansion of the glass is 9.00 ´ 10–6(°C)–1.

a) 0.0176 cm
b) 877.5*10-6 cm
c) 0.093 cm3

6)One mole of an ideal gas, initially at 27 C, is cooled at constant volume so that the final pressure is one-fourth the initial pressure. Determine the temperture of the gas.

T=75 K

R = 8.314 J / mole K