A person has a near point of 20 cm and a far point of 100 cm. Wearing lenses of focal length that correct the nearsightedness, what will the person then have as a near point? Also, what is the power of the corrective lens?
1.17 cm, 1 diopter
2.25 cm, –1 diopter
3.25 cm, 1 diopter
4.17 cm, –1 diopter
2
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The "back emf" of a motor refers to a source of voltage that
a. occurs when the motor runs backwards. b. occurs when the motor is used as a generator. c. is biggest when the current through the motor is biggest. d. is biggest when the motor turns fastest.
When viewed from nearby, a black hole in empty space _____
a. has a funnel shape, extending to the event horizon b. glows in X-rays and gamma-rays from superheated surface c. is invisible d. would look like a dark sphere the size of Earth e. emits blackbody radiation only
Laplace's nebular hypothesis was problematic in that he could not explain ____
a. the different types of planets b. the rotational direction of the planets c. how the Sun had <0.5% of the Solar System's angular momentum d. how one star could come within a close encounter of another star e. how gravity was the dominant force of planet formation
An object initially at rest suddenly explodes in two fragments of masses and that move in opposite directions. If the speed of the first fragment is find the internal energy of the explosion
A) 38 J B) 30 kJ C) 30 J D) 38 kJ