Which body glows with electromagnetic waves?
A) the Sun
B) the Earth
C) you and your classmates
D) all of the above
Answer: D
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A concave mirror has a focal length of 20 cm. What is the magnification if the object and image distances are 10 cm and ?20 cm, respectively?
A. 1 B. 2 C. 1/2 D. 1/4 E. ?1/2
You stand on a scale to measure your weight. The reaction to the force the Earth exerts on you is
A. the force the Earth exerts on the scale. B. the force you exert on the Earth. C. the force the scale exerts on you. D. the force you exert on the scale. E. the force the scale exerts on the Earth.
If the velocity of an object is zero, then that object cannot be accelerating
A) True B) False
Three long, straight, parallel wires each carry a current of 10 A in the positive x direction. If the distance between each wire and the other two is 10 cm, what is the magnitude of the magnetic force on a 20-cm length of either of the wires?
a. 57 mN b. 40 mN c. 69 mN d. 50 mN e. 20 mN