General Physics 201 (PH201) Summer Term 2008

Some Review Questions For Final Exam

Anything from the first half of the term could be on the final. However, the final will clearly be weighted toward the second half of the term. But, since material can build upon itself, it’s easy to incorporate earlier stuff into later problems.

Basic Knowledge (definitions, etc…) This is fundamental, background information that is pretty much required to be able to do well in this class. Most of this will be new to students who have not taken a physics course before. Just memorizing this information is not enough to do well on the tests. You must be able to apply this knowledge in meaningful ways.

1) What is centripetal force and centripetal acceleration? Direction? What is centrifugal force? What is a centrifuge? What does centripetal mean?

2) To what does a time interval of one period refer (in terms of circular motion)? Units?

3) In what two ways is a state of weightlessness achieved?

4) How can artificial gravity be generated?

5) Definitions and formulas for work, kinetic energy, gravitational potential energy? Units? What’s a joule equivalent to in base units? Other units for energy?

6) What is the work-energy theorem?

7) Distinguish between conservative forces and nonconservative forces.

8) What is the Principle of Conservation of Mechanical Energy?

9) How is power defined? Equations? Units? Relationship between watt and horsepower?

10) What is impulse? Momentum? Equations? Units?

11) What is the impulse-momentum theorem?

12) What is the Principle of Conservation of Linear Momentum?

13) Distinguish between internal forces and external forces.

14) What are the collision types - perfectly elastic, elastic, perfectly inelastic, and inelastic? Characteristics? In which cases is KE conserved? When is momentum conserved?

15) Define angular displacement, angular velocity, angular acceleration.

16) What are the basic equations for rotational kinematics?

17) What the heck is a radian?

18) What is tangential speed/velocity? Tangential acceleration?

19) What is torque? What is a lever arm? How is the lever arm measured?

20) What does it mean for an object to be in translation equilibrium? Rotational equilibrium?

21) What is the center of gravity/mass? How is it found?

22) What is moment of inertia? Equations for common objects? Units?

23) How are rotational work, rotational kinetic energy, and angular momentum defined? Equations?

24) What does the Law of Conservation of Angular Momentum tell us?

Applications. These are the skills necessary to solve the basic physics problems expected of you on the tests. The bulk of the tests will be taken from the following:

1) Recognize and solve problems using the work-energy theorem and the Principle of Conservation of Energy. Be able to do this in the absence or presence of non-conservative forces.

2) Solve problems involving the concept of power. Be able to incorporated power into energy problems.

3) Recognize and solve problems using the impulse-momentum theorem.

4) Solve problems using the Principle of Conservation of Linear Momentum. Be able to do this for any type of collision. Be able to do this for problems involving internal forces.

5) Tie any/all of this together with any/all of the old stuff - Newton’s Laws, kinematics equations, etc... Be able to do multi-step problems incorporating different concepts and solution techniques.

6) Apply rotational kinematics equations for constant angular acceleration problems in a manner similar to problems using straight line kinematics equations.

7) Use the relationship between tangential speed and tangential acceleration and angular speed and angular acceleration to compute either from the other.

8) Solve problems using torque where the torque arm can be at any arbitrary angle relative to the line of action.

9) Solve problems for objects that are in rotational equilibrium by the balancing of clockwise and counter-clockwise torques. This includes correctly using center of gravity concept for extended objects.

10) Solve problems involving torque and moment of inertia; solve simple rotational kinetic energy problems.

Review Continued. More sample questions/problems:

1. In terms of impulse, force, change in momentum, explain why a cushioned fall hurts less/does less damage than a fall onto a hard, rigid surface.

2. Does an accelerating object have momentum? Always?

3. There are two ways in which a normal bicycle could have the same momentum as a normal automobile. Explain...

4. To what types of collisions does the Principle of Conservation of Linear Momentum apply?

5. Explain recoil from two points of view, Newton’s Third Law, and Conservation of Momentum. How can recoil be reduced/minimized? What is the effect of holding a rifle tightly against your shoulder (i.e., why does that hurt less than having the gun slightly away from your body)?

6. What does the sign on work mean? Is work a vector quantity? Is kinetic energy? Potential energy? Momentum?

7. Can PE be negative? Can KE be negative? Can delta KE be negative?

8. A 100 kg running back running at 7 m/s is stopped in 0.5 s by a linebacker? What is the running back’s initial momentum? Final momentum? Delta momentum? What impulse is imparted by the linebacker? What force?

9. A jet engine takes in air, heats and compresses it, then ejects it at high speed. If this engine takes in 20 kg of air per second at an intake speed of 100 m/s and ejects it at 500 m/s, what is the thrust of the engine?

10. Two bullets of equal mass are shot at equal velocities at two equal blocks of wood at rest on a smooth, slippery surface (negligible friction). One bullet, made of rubber, bounces off its wood block (heading back in direction it came from.) The other bullet, made of aluminum (aluminium in England!), burrows into its wood block and stays in the block. Which wood block moves off at a higher speed? Why? (The masses are inconsequential to the answer other than the bullets masses are equal and the wood blocks masses are equal. The wood blocks ARE more massive than the bullets.)

11. A 1110 N Superman is hovering in the air. (How DOES he do that?!) Lex Luther launches a 2 kg chunk of kryptonite at him at a speed of 650 m/s. Superman catches it at precisely his own center of mass (so as to not cause any unbalanced torques which would cause him to rotate.) Though Superman violates nearly every law of known physics, he’s not getting away with violating the principle of conservation of linear momentum. What is Superman’s resulting velocity? What is the kryptonite’s original KE? What is the final KE of Superman and the kryptonite? Was KE conserved? Was this collision elastic or inelastic? Perfectly?

12. Same problem, new ending. If Superman would have let the kryptonite bounce off his chest in a perfectly elastic collision, both KE and momentum would be conserved. Simultaneously solve the equations for both conservation of KE and conservation of momentum to find the new velocities of both the kryptonite and Superman. What is the sign on the kryptonite’s final velocity? What does that mean? In which case, problem #11 or #12, does Superman acquire the greatest velocity? (Notice similarity between this last question and question #10...)

13. Rotational examples go here… Torque too…

Main Topics Covered this term:

For the comprehensive part of the test, any of the old (type of) problems are reasonable to expect. Clearly, because of time constraints, it is not possible to have one of every type of problem represented. Problems will be similar to problems from previous tests and homework sets. To keep the volume of problems down, it is likely that a given problem may incorporate several physical principles. MAIN topics covered this term (in chapter order):

* Vectors. Vector addition. Trigonometric solution, graphical solution. Most likely related to some physical problem rather than a stand-alone vector question, e.g., resultant velocity, net force, momentum, etc...

* Applications of the equations for straight line kinematics for objects experiencing constant acceleration in 1-D and 2-D (projectiles.) (Remember falling things and projectiles are experiencing constant acceleration of 9.8 m/s/s...)

* Understanding and application of Newton’s Three Laws in dynamics problems. These problems involve:

- Weight or force of gravity (Newton’s Law of Universal Gravitation?).

- Normal force.

- Tension. Pulling/pushing/applied forces.

- Friction.

- Forces at angles, gravitational force on inclines.

- Forces between two objects via a rope over a pulley.

- Centripetal force.

- Resultant or Net Force, free-body diagrams.

* Understanding and application of the principles of work, energy, and power. These problems can involve:

- Work-energy theorem.

- Kinetic energy, gravitational potential energy.

- Principle of conservation of mechanical energy including conservative and non-conservative forces.

* Understanding and application of impulse-momentum theorem.

* Understanding and application of conservation of linear momentum in “collision” problems. (1D and 2D)

* Applications of the equations for rotational kinematics for objects experiencing constant angular acceleration.

* Understanding and application of equations involved in rotational dynamics problems. These involve:

- Torque.

- Moment of Inertia

- Conservation of Angular Momentum.

- Balance of Forces and Torques in Equilibrium and Non-Equilibrium Problems.

Again, remember the final exam emphasis is the second half of the course.

Things that may be helpful when preparing for this exam include, but aren’t limited to:

- Study/review past homework assignments.

- Work problems other than the assigned suggested problems at the ends of the chapters. (Odd

problems have answers in back of book.)

- Come to office hours with specific questions/problems you would like to have answered.

- Email the instructor for questions that can be answered via email.

- Study with a friend, or friends, or an enemy even, as long as you can help each other.