The speed of a 2.0-kg object changes from 30 m/s to 40 m/s during a 5.0-s time interval. During this same time interval, the velocity of the object changes its direction by 90°. What is the magnitude of the average total force acting on the object during this time interval?
a. 30 N
b. 20 N
c. 40 N
d. 50 N
e. 6.0 N
B
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A wind farm generator uses a two-bladed propeller (see figure) mounted on a pylon at a height of 20 m
The length of each propeller blade is 12 m. A small piece from the tip of the propeller breaks off when the propeller is vertical. At that instant, the period of the motion of the propeller is 1.2 s. The fragment flies off horizontally, falls with negligible air resistance, and strikes the ground at P. (a) How far is point P from the base of the pylon? (b) At what angle with respect to the vertical is the fragment moving just as it strikes the ground at P? What will be an ideal response?
John says that the value of the function cos[w(t + T) + j], obtained one period T after time t, is greater than cos(wt + j) by 2p. Larry says that it is greater by the addition of 1.00 to cos(wt + j). Which one, if either, is correct?
a. John, because wT = 2p. b. John, because wT = 1 radian. c. Larry, because wT = 2p. d. Larry, because wT = 1 radian. e. Neither, because cos(q + 2p) = cosq.
A 9.0-V battery costs $1.49 and will run a portable CD player for 6.0 hours before running down and needing to be replaced
If this battery supplies a current of 25 mA to the player, what is the cost of the energy provided by the battery in dollars per kWh? A) $11/kWh B) $11,000/kWh C) $1100/kWh D) $110/kWh
In Kepler's model of the Universe, what was the purpose of the five regular solids?
a. To differentiate the six planets b. To define the shape of each of the orbits c. To describe the internal shape of each planet d. To be spacers for the orbits of the six planets e. To support the calculations of each orbital period