Q. A boxcar of mass 600 tons at rest becomes uncoupled on a 5.00 grade. If the track is considered to be frictionless, what speed does the boxcar have after 15 seconds?
Q. A radio telescope, whose two antennas are separated by 55 {rm m}, is designed to receive 3.0-{rm MHz} radio waves produced by astronomical objects. The received radio waves create 3.0-{rm MHz} electronic signals in the telescope's left and right antennas. These signals then travel by equal-length cables to a centrally located amplifier, where they are added together. The telescope can be "pointed" to a certain region of the sky by adding the instantaneous signal from the right antenna to a "time-delayed" signal received by the left antenna a time Delta t ago. (This time delay of the left signal can be easily accomplished with the proper electronic circuit.)
If a radio astronomer wishes to "view" radio signals arriving from an object oriented at a 12 degree angle to the vertical , what time delay Delta t is necessary?