Three lenses, each of focal length 90 cm, are placed in contact. What is the focal length of the combination?
A. 27 cm
B. 93 cm
C. 1/30 cm
D. 45 cm
E. 30 cm
E. 30 cm
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A voltage V is applied to the primary coil of a step-up transformer with a 3:1 ratio of turns between its primary and secondary coils. A resistor R connected to the secondary dissipates a power P = 100 W
How much power is dissipated by the same resistor when the ratio of turns in the transformer is changed to 24:1 and the same input voltage is used? A) 12,000 W B) 2400 W C) 24,000 W D) 6400 W E) 100 W
A bullet of mass 0.010 kg and speed of 200 m/s is brought to rest in a wooden block after penetrating a distance of 0.10 m. This process takes 0.02 second. The magnitude of the impulse delivered to the bullet by the block during this time is
A. 0.98 N. B. 2.0 Ns. C. 1.0 Ns. D. zero. E. 4.0 Ns.
A solid metal sphere is 15.0 cm in diameter and has surface of uniform color. When its surface is at 112°C, you measure that it radiates energy at a rate of 71.3 W
What is the emissivity of the surface of this object? Any heat that enters the sphere from the outside environment is negligible. The Stefan-Boltzmann constant is 5.670 × 10-8 W/m2 • K4.
Suppose working outside on a hot day someone generate 450 J of heat each second. If this energy is compensated for by the evaporation of sweat, how much water would be lost in an hour? The latent heat of fusion for water is 334 kJ/kg and for vaporization is 2,200 kJ/kg
a. 4.85 liter c. 0.50 liter b. 0.74 liter d. 1.5 liter