A motorcyclist is moving 24.5 m/s toward a stationary siren, and
hears an 894 Hz sound. What is
the frequency of the siren when
the cyclist is stationary?
(Hint: 894 Hz is the Doppler-shifted
frequency.)
(Speed of sound = 343 m/s)
(Unit = Hz)

Next a skier is pulled by a tow rope up a frictionless ski slope that makes an angle of 15 with the horizontal. the rope moves parallel to the slope with a constant speed of 0.69 m/s. the force of the rope does 800 3 of work on the skier as the skier moves a distance of 8.4 m up the incline. (a) if the rope moved with a constant speed of 2.2 m/s how much work would the force of the rope do on the skier as the skler moved a distance of 8.4 m up the incline? at what rate is the force of the rope doing work on the skier when the rope moves with a speed of (b) 0.69 m/s and (c) 2.2 m/s?

15. one purpose of the tread pattern on a tire is to a reduce tire wear. b. reduce traction c. allow water to flow away from the tire. d. look impressive.

What is the final velocity of the initial velocity of 25 and -50?