When a 0.058 kg tennis ball is served, it accelerates from rest to a speed of 45.0 m/s. The impact with the racket gives the ball a constant acceleration over a distance of 0.440 m. What is the magnitude of the net force acting on the ball?

a. What is the average velocity of the ball?

b. Over what time period was the ball struck?

c. What is the acceleration of the ball?

d. What is the net force on the ball?

e. If the ball had been heavier, but experienced the same change in velocity, would the applied force have to be greater or lesser than before?

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?

Abatter hits a 0.140-kg baseball that was approaching him at 30 m/s and, as a result, the ball leaves the bat at 40 m/s in the reverse of its original direction. the ball remains in contact with the bat for 2.0 ms. what is the magnitude of the average force exerted by the bat on the ball?

Which statements best describe medical uses for radioactive isotopes? check all that apply. radioactive isotopes are used to detect medical problems. high-energy gamma rays are injected into the body. radioactive isotopes are used to treat some diseases. radiation is used to kill cancer cells. radioactive isotopes are directed at tumors from outside the body.