Fisica 1 - tipler

- TiplrChapter 4 Newton’s Laws
Conceptual Problems
1 • While on a very smooth level transcontinental plane flight, your coffee cup sits motionless on your tray. Are there forces acting on the cup? If so, how do they differ from the forces that would be acting on the cup if it sat on your kitchen table at home? Determine the Concept Yes, there are forces acting on it. They are the normal force of the table and the gravitational pull of Earth (weight). Because the cup is not accelerating relative to the ground, the forces are the same as those that would act on it if it was sitting on your table at home. 2 • You are passing another car on a r highway and determine that, relative to you, the car you pass has an acceleration a to the west. However, the driver of the other car is maintaining a constant speed and direction relative to the road. Is the reference frame of your car an inertial one? If not, in which direction (east or west) is your car accelerating relative to the other car? Determine the Concept No. You are in a non-inertial frame that is accelerating to the east, opposite the other car’s apparent acceleration. 3 • [SSM] You are riding in a limousine that has opaque windows that do not allow you to see outside. The car is on a flat horizontal plane, so the car can accelerate by speeding up, slowing down, or turning. Equipped with just a small heavy object on the end of a string, how can you use it to determine if the limousine is changing either speed or direction? Can you determine the limousine’s velocity? Determine the Concept In the limo you hold one end of the string and suspend the object from the other end. If the string remains vertical, the reference frame of the limo is an inertial reference frame. 4 •• If only a single nonzero force acts on an object, does the object accelerate relative to all inertial reference frames? Is it possible for such an object to have zero velocity in some inertial reference frame and not in another? If so, give a