Bob has just finished climbing a sheer cliff above a beach and wants to figure out how high he climbed. all he has to use,
however, is a baseball, a stopwatch, and a friend on the ground with a long measuring tape. bob is a pitcher, and knows that
the fastest he can throw the ball is vo = 91.0 mph. bob starts the stopwatch as he throws the ball (with no way to measure
the ball's initial trajectory) and watches carefully. the ball rises and then falls, and after t; = 0.510 s, the ball is once again
level with bob. bob cannot see well enough to time when the ball hits the ground. bob's friend then measures that the ball
landed a distance of x = 387 ft from the base of the cliff. how high up is bob if the ball started from exactly 5 ft above the
edge of the clift?

Stion 13 of 20 : select the best answer for the question. 13. if a certain mass of mercury has a volume of 0.002 m3 at a temperature of 20°c, what will be the volume at 50°c? a. 0.002021624 m3 b. 0.004021624 m3 c. 0.000010812 m3 d. 0.002010812 m3

The sun generates both mechanical and electromagnetic waves. which statement about those wave is true?

Search coils and credit cards. one practical way to measure magnetic field strength uses a small, closely wound coil called a search coil. the coil is initially held with its plane perpendicular to a magnetic field. the coil is then either quickly rotated a quarter-turn about a diameter or quickly pulled out of the field. (a) derive the equation relating the total charge q that flows through a search coil to the magnetic-field magnitude b. the search coil has n turns, each with area a, and the flux through the coil is decreased from its initial maximum value to zero in a time ∆t. the resistance of the coil is r, and the total charge is q = i∆t, where i is the average current induced by the change in flux. (b) in a credit card reader, the magnetic strip on the back of a credit card is rapidly “swiped” past a coil within the reader. explain, using the same ideas that underlie the operation of a search coil, how the reader can decode the information stored in the pattern of magnetization on the strip. (c) is it necessary that the credit card be “swiped” through the reader at exactly the right speed? why or why not?