What positive effect have supernovae had on the development of life on Earth?
a. Supernovae are the main source of background radiation needed for mutations.
b. Chemical elements necessary for life can only be formed in supernovae
c. The formation of the Sun was triggered by a supernova event.
d. Planets form by accretion of material in the expanding remnant of a supernova.
e. Neutrino bombardment was necessary to form the first simple proteins.
b
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An object moves 10.0 m east in 10.0 s and then returns to its starting point taking an additional 40.0 s. If west is chosen as the positive direction, what is the average speed of the object?
a. 0.4 m/s b. –0.4 m/s c. 10.0 m/s d. 0 m/s e. –10.0
What primary wavelength and corresponding photon energy is emitted by a body at: (a) 400.°C? (b) 800.°C? (c) 1200.°C?
What will be an ideal response?
The loop’s front end has emerged from the field.
A. forward (in the +x direction). B. backward (in the -x direction). C. zero. D. some other direction (specify).
A 200 N box is pushed up an incline that is 5.00 m long and rises 1 m. If the incline is frictionless, then the work done by the pushing force is
A. 336 J. B. 305 J. C. 275 J. D. 200 J. E. 157 J.