A pure sample of 226Ra contains 3.0 × 10^14 atoms of the isotope. If the half-life of 226Ra = 1.6 × 10^3 years, what is the activity of this sample?
a. 13 × 10^10 decays/yr
c. 6.7 × 10^9 decays/yr
b. 9.4 × 10^10 decays/yr
d. 8.7 × 10^10 decays/yr
A
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A coil is wrapped with 300 turns of wire on the perimeter of a circular frame (radius = 8.0 cm). Each turn has the same area, equal to that of the frame. A uniform magnetic field is turned on perpendicular to the plane of the coil. This field changes at a constant rate from 20 to 80 mT in a time of 20 ms. What is the magnitude of the induced emf in the coil at the instant the magnetic field has a
magnitude of 50 mT? a. 24 V b. 18 V c. 15 V d. 10 V e. 30 V
A spaceship moves at a speed of 0.95c away from the Earth. It shoots a star wars torpedo toward the Earth at a speed of 0.90c relative to the ship. What is the velocity of the torpedo relative to the Earth? (The direction in which the spaceship moves is the positive direction.)
a. ?0.34c b. 0.34c c. 0.060c d. ?0.060c e. 0
Describe Couette flow
What will be an ideal response?
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