When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, he doesn't slip off the skateboard because of
A) inertia in motion.
B) momentum change.
C) friction between his feet and the board.
Answer: C
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When the first solid bits in the solar nebula became large enough to be called planetesimals, what caused them to grow larger more quickly?
a. gravity b. friction c. electrical forces d. pressure
Exhibit 13-1
Two blocks of masses m1 and m2 are connected by a light cord that passes over a pulley of mass M, as shown. Block m2 slides on a frictionless horizontal surface. The blocks and pulley are initially at rest. When m1 is released, the blocks accelerate and the pulley rotates.
?
?
Use this exhibit to answer the following question(s).
Refer to . The total angular momentum of the system of the two blocks and the pulley relative to the axis of rotation of the pulley is
a.
proportional to the radius of the pulley.
b.
proportional to the speed of the blocks.
c.
proportional to the length of the string.
d.
to all of the above.
e.
only to (a) and (b) above.
A car starts out when the air temperature is 288 K. The air pressure in the tires is 500 kPa. After driving a while, the temperature of the air in the tires increases to 298 K
What is the pressure in the tires at that point, assuming the volume remains constant? A) 129 kPa B) 483 kPa C) 507 kPa D) 517 kPa E) 532 kPa
Protostars are observable by radio telescopes but hard to detect in visible light because they have ________ and are ________.
A. low surface temperature; very distant B. small size; very distant C. low surface temperature; surrounded by dust D. small size; very hot