Transcript
PHYS 195 Spring 2018 Sample Exam 2
Short Answer. Provide a written explanation for each question. Two or three sentences should suffice.
A box on a ramp that is at an angle ? to the horizontal. As ? is increased from zero, and before the box slips do the following increase, decrease, or remain the same: (a) the component of the gravitational force on the box, along the ramp, (b) the magnitude of the static frictional force on the box from the ramp, (c) the component of the gravitational force on the box, perpendicular to the ramp, (d) the magnitude of the normal force on the box from the ramp, and (e) the maximum value fs,max of the static frictional force?
Two balls are thrown at the same time with the same kinetic energy. If one ball has twice the mass of the other, which has the greater speed and by what factor? Which one can do the most work?
Suppose you lift a suitcase from the floor to a table. Does the work you do on the suitcase depend on (a) whether you lift it straight up or along a more complicated path, (b) the time the lifting takes, (c) the height of the table, and/or (d) the weight of the suitcase?
Exercises. Solve each problem. Show your work.
A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.75 of the person’s regular weight. Calculate the acceleration of the elevator, and find the direction of the acceleration?
28746453683000(a) In the figure shown, if m1 = m2 = 1.00 kg and ? = 30o, what will be the acceleration of the system? (b) If m1 = 1.00 kg and ? = 30o, and the system remains at rest, what must be the value of m2? (c) Calculate the tension in the cord for both cases.
On an icy day, you worry about parking your car sliding out of your driveway, which has an incline of 12o. Your next-door neighbor’s driveway has an incline of 9.0o and your neighbor’s across the street is inclined at 6.0o. The coefficient of static friction between your tires and the ice is 0.15. Which driveway(s) are safe to park in?
At an accident on a level road, investigators measure a car’s skid mark to be 78 m long. It was a rainy day and coefficient of friction was estimated to be 0.38. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes. (Why does the car’s mass not matter?)
(a) A 3.0 g locust reaches a speed of 3.0 m/s during its jump. What is its kinetic energy at this speed? (b) If the locust transforms energy with 40 percent efficiency, how much energy is required for the jump?
A 0.40 kg ball is thrown with a speed of 10 m/s at an angle of ? = 30o. Using conservation of energy, calculate (a) its speed at its highest point, and (b) how high it goes.
A 65 kg hiker climbs to the top of a 3900 m high mountain. The climb is made in 5.0 h starting at an elevation of 2200 m. Calculate (a) the work done by the hiker against gravity, (b) the average power output in watts, and (c) assuming the body is 15% efficient, what rate of energy input was required.
