While standing in a low tunnel, you raise your arms and push against the ceiling with a force of 100 N. Your mass is 70 kg. a. What force does the ceiling exert on you? A. 10 N B. 100 N C. 690 N D. 790 N E. 980 N b. What force does the floor exert on you? A. 10 N B. 100 N C. 690 N D. 790 N E. 980 N

Are the objects described here in static equilibrium, dynamic equilibrium, or not in equilibrium at all? a. A girder is lifted at constant speed by a crane. b. A girder is lowered by a crane. It is slowing down. c. You're straining to hold a 200 lb barbell over your head. d. A jet plane has reached its cruising speed and altitude. e. A rock is falling into the Grand Canyon. f. A box in the back of a truck doesn't slide as the truck stops.

Dave pushes his four-year-old son Thomas across the snow on a sled. As Dave pushes, Thomas speeds up. Which statement is true? A. The force of Dave on Thomas is larger than the force of Thomas on Dave. B. The force of Thomas on Dave is larger than the force of Dave on Thomas. C. Both forces have the same magnitude. D. It depends on how hard Dave pushes on Thomas.

a. A 0.60 kg bullfrog is sitting at rest on a level log. How large is the normal force of the log on the frog? b. A second 0.60 kg bullfrog is on a log tilted $30 ^ { \circ }$ above horizontal. How large is the normal force of the log on this frog?

a. How much force does an 80 kg astronaut exert on his chair while sitting at rest on the launch pad? b. How much force does the astronaut exert on his chair while accelerating straight up at $10 \mathrm { m } / \mathrm { s } ^ { 2 }$?

An astronaut takes his bathroom scale to the moon and then stands on it. Is the reading of the scale his true weight? Explain.