A ball falls from the top of a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building?
A) K is equal to U.
B) K is greater than U.
C) K is less than U.
D) It is impossible to tell.
C
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An object is placed at F in front of a concave mirror with a focal length of 10 cm. What is the position of its image in relation to the mirror and what are its characteristics?
A) = 10 cm, real, smaller than object B) = 10 cm, virtual, smaller than object C) = 20 cm, real, bigger than object D) = 20 cm, virtual, bigger than object E) = ?, real, much bigger than the object
What is the kinetic energy of a 200-kg satellite as it follows a circular orbit of radius 8.0 × 10^6 m around the Earth? (Mass of Earth = 6.0 × 10^24 kg.)
a. 5.0 × 10^9 J b. 1.0 × 10^10 J c. 1.5 × 10^10 J d. 2.0 × 10^10 J e. 2.5 × 10^9 J
The figure shows the orientation of a rectangular loop consisting of 80 closely wrapped turns each carrying a current I. The magnetic field in the region
is (
)mT. The loop can turn about the y axis. If ? = 30°, a = 0.40 m, b = 0.30 m, and I = 8.0 A, what is the magnitude of the torque exerted on the loop?
a.
2.5 N ? m
b.
1.5 N ? m
c.
3.1 N ? m
d.
2.7 N ? m
e.
0.34 N ? m
About how many galaxies are there in the observable universe?
A) roughly (within about a factor of 10) the same as the number of stars in our galaxy B) a few dozen C) a few thousand D) about as many as the number of grains of sand on all the beaches on Earth E) an infinite number