Bert and Ernie are two friends of the same age. Bert visits a nearby star system on a spaceship that travels close to the speed of light while Ernie stays at home. Which of the following will be true on Bert's return to Earth?
A) Ernie will be younger than Bert
B) Ernie will be older than Bert
C) Bert and Ernie will still be the same age
D) Ernie will not have been born
B
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Potential Energy: A +5.0-nC charge is at the point (0.00 m, 0.00 m) and a -2.0-nC charge is at (3.0 m, 0.00 m). What work is required to bring a 1.0-nC charge from very far away to point (0.00 m, 4.0 m)? (k = 1/4??0 = 9.0 × 109 N ? m2/C2)
A. 15 nJ B. 3.6 nJ C. 11 nJ D. 7.7 nJ
One 3.2-kg paint bucket is hanging by a massless cord from another 3.2-kg paint bucket, also hanging by a massless cord, as shown in the figure
a) If the buckets are at rest, what is the tension in each cord?
b) If the two buckets are pulled upward with an acceleration of 1.25 m/s by the upper cord, calculate the tension in each cord.
Appliances with three-pronged plugs compared to those with two-prong plugs are
1.safer to use and connected to ground. 2.no safer to use and ungrounded. 3.more dangerous to use and connected to ground. 4.safer to use and ungrounded.
A refrigerator has a COP of 2.5. If it removes 7.7 MJ of heat in 25. minutes,
(a) what is the minimum power motor to operate the refrigerator? (b) what is its efficiency if it were a reversible engine?