Which of the following is a problem with the estimated age of the universe? There are stars in our galaxy that appear to be over 15 billion years old.

The universe is shrinking, which makes it is impossible to tell how old it is.

There should be more supergiants if the universe is really about ten billion years old.

There are planets in other galaxies that are less than five billion years old.

16. a brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 n on him. the mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20m/s2 size 12{1 "." "20"" m/s" rsup { size 8{2} } } {} backward. (a) what is the force of friction between the losing player’s feet and the grass? (b) what force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg? (c) draw a sketch of the situation showing the system of interest used to solve each part. for this situation, draw a free-body diagram and write the net force equation.