In a therapeutic clinical trial, both the experimental group and the control group are composed of patients who have the disease for which a therapy is being tested.
a. true
b. false
a. true
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Suppose you have 10 helium-filled party balloons tied to a digital camera, so you can take photos of the core of a storm. With 10 balloons the camera will slowly but surely rise. As a storm approaches the atmospheric pressure drops. Assuming the air temperature and density are the same, the volume of each balloon will increase. When you let go, the speed of ascent will be ________.
What will be an ideal response?
A stopping potential of 0.50 V is required when a phototube is illuminated with monochromatic light of wavelength 590 nm
Monochromatic light of a different wavelength is now shown on the tube, and the stopping potential is measured to be 2.30 V. What is the wavelength of this new light? (c = 3.00 × 108 m/s, e = - 1.60 × 10-19 C, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J) A) 320 nm B) 300 nm C) 340 nm D) 360 nm E) 410 nm
Stellar cores, near the end of a star’s lifetime, produce iron by fusion. The reason stellar cores don’t go past iron is that
A. iron in stellar cores tends to spontaneously fission. B. Iron is the most dense material in solid form C. iron nuclei are the most tightly bound per nucleon. D. iron is ferromagnetic. E. iron is heavy.
Suppose a highway curve is properly banked to eliminate friction for a speed of 45 mph. If your tires were bald and you wanted to avoid sliding on the road, you would have to drive
A) somewhat below 45 mph. B) somewhat above 45 mph. C) at exactly 45 mph.