Suppose that we have a sample of 20 atoms of radioactive potassium which decays by half every 1.3 billion years into calcium and argon at ratios of 9:1, respectively. How many atoms of calcium do you expect to find in this sample after 1.3 billion years?
A. 9
B. 18
C. 1
D. 2
Answer: A
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The acceleration of a vertically-thrown ball at the top of its path is
A) zero. B) 10 m/s2. C) between zero and 10 m/s2. D) dependent on the mass of the ball.
Buoyancy: A 200-kg flat-bottomed boat floats in fresh water, which has a density of 1000 kg/m3. If the base of the boat is 1.42 m wide and 4.53 m long, to what depth is the bottom of the boat submerged when it carries three passengers whose total mass is 257 kg?
A. 7.10 cm B. 7.53 cm C. 7.95 cm D. 8.52 cm
In a certain region of space, a uniform electric field is in the x direction. A particle with negative charge is carried from x = 20.0 cm to x = 60.0 cm. The electric potential energy of the charge-field system:
1.increases. 2.remains constant. 3.decreases. 4.changes unpredictably.
A 0.28-kg stone you throw rises 34.3 m in the air. The magnitude of the impulse the stone received from your hand while being thrown is
a. 0.27 N s. b. 2.7 N s. c. 7.3 N s. d. 9.6 N s. e. 34.3 N s.