PHYS TEST

Fall 2019 - Why Things Move - Test II (100 points total)

Important: This exam is to be done independently by each student. No outside help from other students, faculty or outside individuals is allowed. ALL EXAMS are compared to make sure students do independent work. Students that are found to have worked with other students or receive outside help will receive a severe penalty. DO NOT CUT AND PASTE your answers from the articles or other sources.

This exam is due by Monday, November 25th 11:55 PM. Late exams will be penalized for every day they are submitted after the deadline.

Short Answer Questions (5 points each, 100 points total)

Use complete sentences and details to answer all but the quantitative questions. Mathematical calculations are recommended on your answer sheet for quantitative problems (questions with numbers).

1. Convert the following into radians

a. 1.0° b. 10.0° c. 45.0° d. 180° e. 270°

2. Convert the following into angular velocity in radians per second?

a. 33 rpm b. 78 rpm c. 120 rpm d. 1 rotation per second e. 30 rotations per second

3. Look at the overhead diagram of the door on a hinge. Force A, B and C are all equal. Rank each force from highest to lowest torque on the hinge of the door.

4. A force of 200 N is applied to a wrench as shown in the diagram below. What is the torque is the force is applied 0.600 m from the pivot point of the nut? Is the torque positive or negative?

5. In the diagram below a 25.0 kg weight is supported by the bicep muscle. What is the torque (in units of Nm) on the elbow joint due to the 25 kg weight?

.

6. What is the force (in units of N) of the bicep muscle to support the weight?

7. According to Newton’s Universal Law of Gravitation, any object with mass exerts a force on any other object with mass. Calculate the gravitational force between two people (both mass of 80 kg), 1 meter away from each other. Does this explain why we don’t feel the gravitational force from all but the Earth?

8. Explain why Saturn is almost 100 times more massive than the Earth, however, the acceleration of gravity on the top of Saturn’s clouds (no solid surface) is about the same as the gravity at the surface of the Earth.

9. In 2014, a pair of astronomers offered proof of a distant planet orbiting the Sun using the orbits of Pluto-like bodies at the edge of the Solar System. The hypothetical planet nine may orbit well beyond the orbit of Neptune, 700 times further from the Sun than the Earth. What would the approximate period of this orbit be according to Kepler’s third law?

10. The Boeing 777-300ER uses two of the largest jet engines ever built (GE-90) to generate thrust? It’s massive GE-90 has been able to generate 569 kN (5.69 x 105 N) of force during a “red-line” test. Normally maximum thrust is 450 kN (4.50 x 105 N). If the Jet has two of these engines, how much work do these engines do as it accelerates 2.0 km (2,000 m) down the runway?

11. The 777 has a cruising altitude of 43,000 ft (13,100 m) at a speed of 560 mph (250 m/s). The operational mass of the 777 is 180,000 kg. What is the gravitational potential energy and the kinetic energy of this aircraft at cruising altitude?

12. A scale is used to measure the weight of an object. The scale can measure weights up to a maximum of 200 N. If the spring compresses 5.0 cm (0.0050 m) at this maximum weight, what is the spring constant of the spring in this scale?

13. A pendulum on a mechanical clock is designed to have a period of precisely 0.50 seconds to keep time. How long should this pendulum be to have a period of 0.50 s?

14. A cannon used by Napoleon’s forces had a mass of 1,500 kg and could fire a 5.0 kg shell with a velocity of 400 m/s (nearly the speed of sound). What is the momentum and kinetic energy of the shell?

15. If the cannon above were not secured to the ground, what would its recoil velocity be for these conditions?

Essay (2 paragraph minimum): Car Safety and Momentum (25 points) – Please reread the chapter on momentum and impulse. Explain how safety features such a seat belts, crumple zones and air bags can reduce injury. Do this in the context of momentum, impulse, interaction time and force. If you need to draw diagrams or graphs, please feel free to include them in your discussion.