Study questions for Physics P201 by Topic

Numbers and approximations

• What is dimensional analysis, how is it useful?
• What is the difference between dimension and precision?
• What is the difference between precision and accuracy? (Check the lab manual appendix for this one.)
• What is the difference between dimension and unit?
• If we multiply several numbers with differing precision, which one determines the precision of the answer?
• What is an Order-of-Magnitude calculation good for?
• Why is estimation an important part of physics (aren't scientists always interested in exact answers)?
• Be sure you know how to convert from one set of units to another.

Motion in one dimension:

• What is the difference between velocity and acceleration?
• What is the slope of a position versus time graph?
• What is the slope of a velocity versus time graph?
• Why is graphing data useful?
• What is the relationship between a graph of a straight line and the mathematical equation y=mx+b?
• What is the difference between instantaneous velocity and average velocity?
• Why is gravitational acceleration (9.8 m/s²) the same for any object?
• Of the four equations of motion in this chapter, which ones are only good for constant speed?

Vectors:

• Why do we need vectors in physics?
• What is the difference between a vector and a scalar?
• What is the difference between displacement and distance?
• What is the difference between speed and velocity?
• How do you add (or subtract) vectors by the trigonometric method? By the graphical method?
• Can the magnitude of a vector be negative?
• Can the components of a vector be negative?
• How is the addition of vectors different from the addition of scalars?
• What is the difference between the components of a vector and the magnitude of a vector? Is it possible for the magnitude to equal the value of a component? When could this occur?

Motion in Two dimensions:

• Why are vectors useful when talking about projectile motion?
• What is the velocity of an object thrown straight upward at the top of its trip?
• What is the acceleration of an object thrown straight upward at the top of its trip?
• Draw a picture of the velocity vector of a projectile shot at 45 degrees for several points along its trajectory. When is the velocity vector horizontal?

Newton's Laws:

• Why does a runner accelerate if Newton's third law is correct ? Isn't the net force zero in this case ?
• What is the difference between mass and weight?
• If the total force (sum of all forces acting in each direction) is zero on an object can it have a non zero velocity? Explain.
• Why is an understanding of vectors very important for understanding this material?
• If you want to stop a car in a minimum distance, why is it better not to press on the brakes so hard that the tires slide?
• What information do you need to be able to answer the following question correctly: Which moves faster, a 10,000kg car with a net force of 5N or a 10,0000kg car with a net force of 10N?
• If the total force (sum of all forces acting in each direction) is zero on an object can it have a non zero velocity ? Explain.
• According to Newton's second law, F = ma. Give an example where the forces on an object are not zero but the acceleration is zero.
• A car is traveling at a constant 60 mph. What is the net force acting on the car? Explain.
• Explain why it is not possible for an object to travel in a curved path if the net force on it is zero.

Mechanical Energy:

• Where do you measure the h from in PE=mgh?
• For work lost due to friction, is the energy really lost? What happens to it?
• When a baseball is being thrown, is any work done on the ball while it is in contact with the pitchers hand? Explain.
• When a baseball is being thrown, is any work done on the ball after it has left the pitchers hand? Explain.
• Does the gravitational force of the earth do work on a moving satellite?
• Is kinetic energy a vector or not?
• Is gravitational potential energy a vector or not?
• What is the difference between work and power?
• Does an electric utility sell power or work?

Momentum:

• What is the difference between momentum and kinetic energy?
• Which has a larger change in momentum, a ball of putty that hits a wall and sticks or a golf ball that bounces back with the same speed (assume they have the same mass and initial velocity)? Explain.
• What is the difference between elastic collisions and inelastic collisions?
• How are impulse and momentum related?
• When do you use the impulse equation and when can you use conservation of momentum?
• Which are always conserved in a collision: total energy, kinetic energy, potential energy, momentum?

Circular motion:

• What is the difference between centripetal acceleration and tangential acceleration?
• Circular motion sometimes has tangential acceleration but always has centripetal acceleration. Why?
• How does the linear velocity of a point on the edge of a rotating circle relate to its angular speed?
• How does the linear acceleration of a point on the edge of a rotating circle relate to its angular acceleration?
• How does the linear velocity of a point on a rolling wheel (which is not slipping) relate to the speed of the center of the wheel?
• You are looking down on a turning merry-go-round. A ball originally stuck to the surface of the merry-go-round comes loose. Draw a picture of the path of the ball as it leaves the turning merry-go-round.
• The earth and a satellite are attracted towards each other by the gravitational force. If someone asks you "What keeps a satellite up in its orbit around the earth?" how would you respond?
• Why is it easier to loosen a bolt if you hold the end of the wrench rather than the middle?
• Does the string in the laboratory we did on circular motion produce any torque on the rotating mass when traveling at a constant velocity? Why or why not?

Solids and Fluids; Pressure:

• Why does a battleship floats even though it is made of iron which is more dense than water?
• Why is a narrow shoulder strap on a backpack more uncomfortable than a broad strap?
• Describe why some things float without using the word density.
• Why is the thickness of a dam greater at the bottom than at the top?
• A boat floats in a swimming pool filled with water. A person on the boat throws the anchor into the pool where it sinks. What happens to the level of the water compared to the side of the boat (does the boat rise or sink)? What happens to the level of the water compared to the side of the pool (does the water level rise or sink)? Explain what happened.

Thermodynamics:

• What are the first and second laws of thermodynamics?
• Does the temperature of something always go up if heat is added? Explain.
• What are the four means of heat transfer?
• What interesting property of a constant volume gas thermometer caused scientists to pick -273C as absolute zero Kelvin?
• What is the purpose of finding the triple point of water?
• How does an atomic theory of matter explain evaporative cooling, thermal expansion, Brownian motion, change of phase, and surface tension?
• What is the difference between heat and temperature in microscopic terms?
• What is the classical microscopic interpretation of absolute zero and why is it incorrect?
• How are pressure and temperature related on a microscopic level?
• What is a heat engine? Are Fuel cells heat engines?
• Why can the efficiency of a heat engine never be 100%?
• How is the concept of disorder related to the other statements of the second law of thermodynamics found in your book?
• The second law claims that all processes lead to more disorder. How then do living organisms which start from simple cells develop highly organized structures?
• How do the two statements "You can't get something for nothing." and "You can't even break even." relate to the first and second laws of thermodynamics?

Waves:

• What is the difference between transverse, longitudinal and rotational (tortional) waves?
• What is meant by the superposition of waves?
• Pitch in a sound wave corresponds to which numerical quantity?
• What quality does frequency tell you about for visible light?
• How are the Doppler effects for sound and light similar? Different?
• What happens to the Doppler effect when sound or light from a moving source is reflected from a stationary object? What about reflection from a moving object?