2. Use the v-t graph of the toy in Figure 9 to answer these questions.
a. When is the train's speed constant?
b. During which time interval is the train's acceleration positive?
c. When is the train's acceleration most negative?

Because the sun is the biggest and if the sun orbits the earth we will be dead probably

Answer(b) both involve the use of levers;

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.