Physics H131: Problem Set #4

Two-Minute/Short-Answer Problems

Remember to give a good explanation, no longer than two sentences.

• C5T.9: What would happen if the heavy puck initially did not move northward?
• C6T.3: What determines the final speed of the rock? How does the direction of the initial velocity enter (or does it?)?

Chapter C5 Problems

• C5S.4: Which mechanism controls whether or not the rocket keeps accelerating? Does this mechanism depend on the velocity of the exhaust relative to the asteroid?
• C5S.8: Think about the properties of a "line drive" -- is this a 2- or a 3-dimensional problem? What role does gravity play in this problem? What is your system and its degree of isolation? Can you apply momentum conservation? How do you apply it in this case?

Chapter C6 Problems

• C6B.1: Do the directions matter? Why? How does kinetic energy depend on mass and velocity?
• C6S.1: How does the kinetic energy depend on speed? If speed increases by 40 percent, by how many percent does the kinetic energy increase?
• C6S.6: What is your system and its degree of isolation? How does the potential energy difference depend on your and the Frisbee's horizontal position? Does it matter at which angle the ball hits the Frisbee?

"The Challenge" (Extra Credit)

• C5A.1: Recall the discussion in class: Consider a tiny time interval delta t (or dt) at an arbitrary point in time t (but not at t=0) during which a tiny amount dm of fuel is burnt. Apply momentum conservation at time t and time t + delta t. How does the change in the mass of the rocket relate to the rate at which fuel is burned?