Name Student ID Phys121 Win2011

Transcription

1 (1) (3 pts) The airplane in the figure below is travelling at a constant speed and at a fixed altitude with its engines providing forward thrust. Which of the free-body diagrams below best represents the forces acting on the airplane? (2) (6 pts) The airplane is flying horizontally at a constant speed of 850 km/h. It banks at 30 degrees to make a turn. The angle is such that the plane does not fall or rise in altitude. What is the radius of the turn? Use g = 10 m/s 2. A) 6.8 km B) 9.9 km C) 20 km D) 82 km E) 128 km

2 (3) (4 pts) A camper hangs a m = 26-kg pack between two trees using two separate ropes of different lengths. What is the tension in the rope on the right? Use g = 10 m/s 2. A) 63 N B) 125 N C) 183 N D) 221 N E) 250 N (4) (2 pts) The pack hangs such that its bottom is a distance h above the ground. If both ropes suddenly break and the pack is dropped to the ground where it lands and stops, the net work done by gravity on the pack is A) mgh B) -mgh C) zero (5) (6 pts) A forklift truck pushes a piano, secured inside a cradle, at a constant speed up a ramp raising it a distance h. The piano and box have a total mass m and the coefficient of kinetic friction between the box and the ramp is K. If h = 1.5 m, m = 800 kg, and K = 0.6, what is the work done by the forklift on the piano to raise the piano to the top of the platform if the ramp is at an incline angle of = 20 as shown? Use g = 10 m/s 2. A) 12 kj B) 15 kj C) 21 kj D) 32 kj E) 44 kj

3 Checkpoint Questions Revisited (6) (2 pts) A block slides on a table pulled by a string attached to a hanging weight. In case 1 the block slides without friction and in case 2 there is kinetic friction between the sliding block and the table. In which case is the tension in the string the biggest? A) Case 1 B) Case 2 C) Tensions are the same (7) (2 pts) A box sliding on a horizontal frictionless surface runs into a fixed spring, compressing it a distance x 1 from its relaxed position while momentarily coming to rest. If the initial speed of the box were doubled, how far, x 2, would the spring compress? A) B) C)

4 For the next 2 problems, use the sketch below of the 1-D potential energy function U(x) (8) (3 pts) What is the approximate value of the force at x = 22 m? A) -40 N B) -10 N C) 0 N D) 10 N E) 40 N (9) (2 pts) Where is the force equal to zero? A) 0 < x < 10 B) x = 10 C) 15 < x < 18 D) only at x=5 and x = 25 E) nowhere

5 Name St. ID No. Phys. 121 W11 (print) Last First A cart with a mass of 20 kg is at rest on a frictionless table. An incoming cart with a mass of 5 kg has sticky putty attached to its front surface and has a speed of 6 m/s. When the carts collide they stick together. 10. (2 pts) What is the initial momentum (kg-m/s) of this system? (2 pts) What is the initial kinetic energy (Joules) of this system? (2 pts) What is the speed (m/s) of the center-of-mass of this system? (2 pts) After the carts stick together what is their speed (m/s)? (3 pts) After the carts stick together what is the kinetic energy (Joules) of the system?

6 F (N) x (m) A particle has mass m = 0.5 kg. The force on it is shown in the plot above. A positive force is directed toward larger x. The particle has zero velocity at x = (4 pts) The average power (Watts) supplied while the particle moves from x = 0 to x = 1 meter is: (4 pts) The kinetic energy (J) of the particle at x = 4 m is: These are two identical ramps. On each ramp a block sits at rest. The blocks are identical except that block 1 has a coefficient of static friction µ 1 = 0.3 and block 2 has a coefficient of static friction µ 2 = (4 pts) What is the ratio of the frictional force f 2, on block 2 to the frictional force f 1, on block 1? f 2 f 1 = A. 5/3 B. 3/5 C. 1

7 use g = 10 m/s 2 for convenience A block of mass M = 0.25 kg, falls from rest from a height h, above the top of a spring. The ideal spring is at equilibrium and has a spring constant k = 300 N/m. The mass hits the spring which starts to compress. When the spring compresses 0.1 m the block is no longer moving. 18. (6 pts) What is the kinetic energy (Joules) of the mass when it hits the spring?