fall07 Exam.pdf

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University of Toronto Mississauga
Wagih Ghobriel

Student Name: Student Number: UNIVERSITY OF TORONTO MISSISSAUGA Fall Term Test PHY135Y5Y “Introductory Physics” Instructor: W. Ghobriel Duration: 3 hours Held on Friday 21 Dec, 2007, 8:00–11:00 am at SE Cafe Aids allowed: Any calculators and the provided sheet of constants and formulas. You are not allowed to bring your own prepared sheet of formulas or information. It is an academic offence Duration: 3 hoursossess the following items at their examination desks: cell phones, pagers of any kind, IPODs, MP3 players, wristwatch computers, personal digital assistants (e.g., palm pilots) or any other device that is electronic. If any of these items are in your position now, put examination begins. No penalty will be imposed. A penalty WILL BE imposed if any of these items areore the kept at your examination desk. • TUTORIAL SESSION (MARK ONE) • Mon TUT0101 14:00 – 16:00 pm Tue TUT0201 14:00 – 16:00 pm Wed TUT0301 14:00 – 16:00 pm Thu TUT0401 16:00 – 18:00 pm Fri TUT0501 14:00 – 16:00 pm Tue TUT0601 16:00 – 18:00 pm Thu TUT0701 16:00 – 18:00 pm Notes to students: o The Fall Term Test constitutes 20% of the whole mark of PHY135Y. o Consists of twenty five (25) equally–valued problems. o Choose only one answer in each multiple-choice problem. o The exam consists of 15 pages, including the front page. The formula sheet is provided, separately. PHY135Y5Y Fall Term Test 21 Dec, 2007 page 2 of 15 Student Name: Student Number: (1) A block is at rest on a rough inclined plane and is connected to an object with the same mass as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coefficient of static friction between the block and the plane is s ; and the coefficient of kinetic frictionk.s What is the magnitude of the static frictional force acting on the block? m m (a) mg sin (b) mg cos (c) mg (1 cos ) (d) mg (1 sin ) (e) mg (2) In problem (1), if the rope were cut between the block and the pulley, what would be the magnitude of the acceleration of the block down the plane? (a) g (b) g k sin (c) g kcos (d) g(tan k sin ) (e) g(sin kcos ) continued on next page 3 PHY135Y5Y Fall Term Test 21 Dec, 2007 page 3 of 15 Student Name: Student Number: (3) Two blocks rest on a horizontal frictionless surface as shown. The surface between the top and bottom blocks is roughened so that there is no slipping between the two blocks. A 30-N force is applied 5 kg to the bottom block as suggested in the figure. What is the minimum 30 N coefficient of static friction necessary to keep the top block from 10 kg slipping on the bottom block? (a) 0.05 (b) 0.10 (c) 0.20 (d) 0.30 (e) 0.40 (4) The wheels of an automobile are locked as it slides to a stop from an initial speed of 30.0 m/s. If the coefficient of kinetic friction is 0.200 and the road is horizontal, how long does it take the car to stop? a. 6.00 s b. 7.57 s c. 15.3 s d. 22.5 s e. 30.0 s continued on next page 4 PHY135Y5Y Fall Term Test 21 Dec, 2007 page 4 of 15 Student Name: Student Number: (5) A lamp of mass m hangs from a spring scale that is attached to the ceiling of an elevator. When the elevator is stopped at the fortieth floor, the scale reads mg. What does it read as the elevator slows down to stop at the forty-fifth floor? (a) more than mg (b) less than mg (c) mg (d) zero (e) one cannot tell without knowing how fast the elevator is stopping. (6) An automobile is moving toward the east at 50 km/h, and the wind North A is from the north at 50 km/h. Which vector in the figure represents the wind velocity as observed by a passenger in the car? H B (a) B (b) H (c) D (d) A (e) F West East G C D F South E continued on next page 5 PHY135Y5Y Fall Term Test 21 Dec, 2007 page 5 of 15 Student Name: Student Number: (7) Consider a satellite in a circular orbit around the Earth. If it were at an altitude equal to twice the radius of the Earth, 2R E how would its speed v be related to the Earth’s radius R , and Ehe magnitude g of the acceleration due to gravity on the Earth’s surface? gR gR (a) v2 gR E (b) v 2 2gR (c) v2 gR E (d) v 2 E (e) v2 E 9 E 3 4 2 (8) A rock is whirled on the end of a string in a horizontal circle of radius R with a constant period T. If the radius of the circle is reduced to R/2, while the period remains T, what happens to the centripetal acceleration of the rock? a. It remains the same. b. It increases by a factor of 2. c. It increases by a factor of 4. d. It decreases by a factor of 2. e. It decreases by a factor of 4. continued on next page 6 PHY135Y5Y Fall Term Test 21 Dec, 2007 page 6 of 15 Student Name: Student Number: (9) A block slides from point A down a frictionless curve to point B. After the block passes point B, a friction force opposes the motion of the block so that it comes to a stop 2.5 m from B. Calculate the A coefficient of kinetic friction between the block and the surface after position B. 1 m (a) 2.5 (b) 0.40 (c) 0.20 (d) 0.40 N (e) 0.10 B (10) A student (mass m = 63 kg) falls freely from rest and strikes the ground. During the collision with the ground, he comes to rest in a time of 0.01 s. The average force exerted on him by the ground is +18000 N, where the upward direction is taken to be the positive direction. From what height did the student fall? Assume that the only force acting on him during the collision is that due to the ground. (a) 0.24 m (b) 0.32 m (c) 0.42 m (d) 0.58 m (e) 0.65 m continued on next page 7 PHY135Y5Y Fall Term Test 21 Dec, 2007 page 7 of 15 Student Name: Student Number: −2 (11) A 1.00x10 kg bullet is fired horizontally into a 2.50-kg wooden block attached to one end of a massless, horizontal spring (k = 845 N/m). The other end of the spring is fixed in place, and the spring is unstrained initially. The block rests on a horizontal, frictionless surface. The bullet strikes the block perpendicularly and quickly comes to a halt within it. As a result of this completely inelastic collision, the spring is compressed along its axis and causes the block/bullet to oscillate with amplitude of 0.200 m. What is the speed of the bullet v? oscillation with unstrained k = 845 N/m spring amplitude of 0.200 m Initial position m v (a) 221 m/s (b) 419 m/s (c) 629 m/s (d) 891 m/s (e) 921 m/s
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