When a ball rises vertically to a height h and returns to its original point of projection, the work done by the gravitational force is
a. 0.
b. ?mgh.
c. +mgh.
d. ?2mgh.
e. +2mgh.
a
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The galactic _______________ contains very little gas and dust, old stars, and globular clusters
Fill in the blank(s) with correct word
Refracting Telescope: A student constructs an astronomical telescope and wishes it to have a magnification of 10. If the telescope has an objective lens of focal length 0.50 m, what must be the focal length of the eyepiece?
A. 2.5 cm B. 5.0 cm C. 10 cm D. 25 cm
Conservation of Momentum: A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the momentum during the collision are correct? (There could be more than one correct choice.)
A. The momentum of the truck is conserved. B. The momentum of the car is conserved. C. The car and the truck must undergo the same change in speed. D. The momentum of the car and the momentum of the truck are each conserved. E. The momentum of the car-truck system is conserved, but the momentum of each one separately is not conserved.
When a beam of light, originally traveling in air, enters a piece of glass having an index of refraction of 3/2, its speed
A) increases by a factor of 3/2. B) is reduced to 2/3 its original value. C) is unaffected.