A car starts from rest and reaches 20 m/s in 5 seconds. The average acceleration of the car is
A. 1.0 m/s2.
B. zero m/s2.
C. 4.0 m/s2.
D. 10.0 m/s2.
E. 2.0 m/s2.
Answer: C
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A helicopter stays aloft by pushing large quantities of air downward every second. What mass of air must be pushed downward at 35.0 m/s every second to keep a 1 500-kg helicopter aloft?
a. 42.9 kg b. 420 kg c. 430 kg d. 410 kg e. 415 kg
If 
= 6.0, 
= 5.0, and ? = 40°, determine the scalar product of the two vectors shown.
?
?
A. +19
B. +23
C. ?19
D. ?23
E. +30
Which of the following statements applies in the final moments of the life of high-mass stars?
A. Around their cores, they have a series of nested shells, each made of a heavier element than the one surrounding it. B. The core temperature is about 2 billion degrees. C. Their outer layer is mainly hydrogen and helium. D. They have iron cores. E. All of these choices are correct.
After a supernova event, what is left behind?
A) always a white dwarf B) always a neutron star C) always a black hole D) either a white dwarf or a neutron star E) either a neutron star or a black hole