Velocity: A bat, flying toward the east at 2.0 m/s, emits a shriek that is reflected back to it from a wall that is 20.0 m in front of the bat at the instant the shriek is emitted. Sound travels at 340 m/s in the air. How many milliseconds after emitting the shriek does the bat hear the reflected echo from the wall?
Fill in the blank(s) with the appropriate word(s).
117 ms
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A force of 5.3 N is needed to hold on to an umbrella in a strong wind. If the air molecules each have a mass of 4.7 ×10-26 kg,
and each one strikes the umbrella (without rebounding) with a speed of 2.0 m/s in the same direction, how many molecules strike the umbrella each second? Assume that the wind blows horizontally so that the gravitational force exerted on the air molecules can be neglected.
Two dogs, Rover and Fido, run on a level frictionless surface. Rover runs eastward with a momentum of 24 kg . m/s, and Fido runs northward with momentum 10 kg . m/s. They make a sudden perfectly inelastic collision
What is the magnitude of their combined momentum after the collision? A) 14 kg . m/s B) 34 kg . m/s C) 26 kg . m/s D) It cannot be determined without knowing the masses and velocities of the dogs.
Jadeen says that you can increase the resistance of a copper wire by hammering the wire to make it narrower and longer. Arnell says that you can increase its resistance by heating the wire. Which one, if either, is correct, and why?
a. Arnell, because the resistivity of the wire increases when it is heated. b. Arnell, because the resistivity of the wire decreases when it is heated. c. Jadeen, because the resistivity of a wire is inversely proportional to its area and directly proportional to its length. d. Jadeen, because the resistivity of a copper wire does not decrease when it is hammered. e. Both are correct because (a) and (d) are both correct.
Assuming you are sitting still as you take this quiz, how would you draw your own worldline on a spacetime diagram?
A) a straight, vertical line B) You would not have a worldline because you are not moving. C) a straight, horizontal line D) a diagonal line