In: Physics
1.) A speedboat can travel across a lake (no current) with a speed of 120 km/h. How much time would it take this boat to travel 8.5 km upstream on the Spey River in Scotland, against a current with a speed of 16 m/s? A 4.3 minutes B 5.4 minutes C 6.5 minutes D 8.2 minutes E None of these.
2.) A radar antenna that measures 12 meters from tip to tip (see the figure below) rotates about its midpoint at a rate of 120 revolutions per minute. What is the tangential speed of either tip of the antenna?
A 12 m/s
B 75 m/s
C 150 m/s
D 4.5 x 103 m/s
E None of these is correct
3.) To avoid injury, the pilot of a high-performance jet should never be subjected to a force greater than eight times her or his weight. If an F-35A jet is in a steep dive, traveling with a speed of 2.0 x 102 meters per second, what is the minimum radius of curvature r with which the pilot can safely pull out of the dive? (See the figure. Assume that the pilot is entirely supported by a contact force exerted by her or his seat.)
A 2.9 m
B 510 m
C 580 m
D 4100 m
E None of these is correct.