Why do Newton's Laws show a force must be acting on the planets?
What will be an ideal response?
The planets are moving in elliptical orbits (not a straight line). According to First Law, if no force acts on the body, it must move in a straight line. Since the planets do not, there must be a force acting on them.
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General Questions: A 20-ton truck collides with a 1500-lb car. Which of the following statements must be true?
A. During the collision, the force on the truck is greater then the force on the car. B. During the collision, the force on the truck is equal to the force on the car. C. During the collision, the force on the truck is smaller than the force on the car. D. The truck did not slow down during the collision, but the car did. E. The car did not slow down during the collision, but the truck did.
Energy in Nuclear Reactions: Consider the nuclear reaction 
N + 
He ? 
O + 
H. The known atomic masses are
N: 14.003074 u
/>He: 4.002603 u
H: 1.007825 u
O: 16.999131 uWhat is the Q-value (or reaction energy) of this reaction? (1 u = 931.5 MeV/c2)
A. -1.191 MeV
B. -2.020 MeV
C. -6.725 MeV
D. -9.055 MeV
Consider a situation where you exert a force F on a crate of mass m, moving it at a speed v a distance d across a floor in a time interval t. The quantity Fd/t is
a. the kinetic energy of the crate b. the potential energy of the crate c. the linear momentum of the crate d. the work you do on the crate e. the power you supply to the crate
Based on Mercury's peak temperature of about 700 K, what would the average molecular speed of carbon dioxide be? How does this compare to Mercury's escape velocity? If Mercury's atmosphere initially had substantial carbon dioxide, in line with what
is believed about the early atmospheres of the other terrestrial planets, do you think Mercury would have retained this atmosphere? Why/why not? Would your answer change if you considered only Mercury's coldest regions that are around 125 K?