Tom is 20 years old when he boards a spaceship that flies at 0.800c toward planet x which is 12 lightyears away. left behind on earth is his twin brother tim. upon reaching planet x, tom immediately turns back and returns to earth at a slower speed of 0.600c. what is the biological age of tim upon tom's arrival on earth?
a. 55 yrs old
b. 45 yrs old
c. 40 yrs old
d. 50 yrs old

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

Which statement is true? a. kepler's laws apply only to the motion of earth. b. kepler's laws can be used to predict eclipses. c. kepler's laws are true for a central force that is directly proportional to distance. d. kepler's laws can be deduced from newton's laws of motion and gravity.

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.