An object is not accelerated if
A) it is acted upon by an external influence.
B) its speed remains unchanged while its direction of motion changes.
C) its speed and its direction of motion are both unchanging.
D) its speed changes while its direction of motion remains unchanged.
E) both answers B and D are correct.
C
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Which forming technique is best suited to producing cobalt-tungsten carbide cutting tools?
(a) Hot isostatic pressing of powder (b) Investment casting (c) Forging (d) Superplastic forming
The cosmic background radiation
a. has a blackbody spectrum. b. has its peak emission in the microwave band. c. corresponds to a blackbody at a temperature of 2.726 kelvins. d. all of the above
A box slides up an incline with an angle of elevation ?. When the box reaches its maximum distance up the incline it stops and does not slide down the incline due to friction. What is the minimum value of the coefficient of static friction for this to occur?
a. ?s = tan? b. ?s = sin? c. ?s = cos? d. ?s = 1
The diagram above shows the life track of a 1 MSun protostar from the time it first begins to form until it reaches the main sequence, with four stages labeled. What is happening to the protostar's surface temperature and luminosity during Stage 4, when its life track moves straight down to join the main sequence?
A) Its surface temperature and luminosity increase. B) Its surface temperature increases, and its luminosity decreases. C) Its surface temperature and luminosity decrease. D) Its surface temperature decreases, and its luminosity increases. E) Its surface temperature and luminosity remain the same.