Why can't the efficiency of a heat engine be 100%?

The time separating high tides is 12 hours and 25 minutes. A high tide occurs at 3:10 p. m. The next low tides occur at 9:30 AM and 9:00 PM the next day. True or False? Provide calculations.

When the wood block is dropped in the water and settles so that it floats and is no longer bobbing up and down, how do the buoyant force and gravity compare?

How many neutrons does Krypton (Kr) have?

Tina is looking out a window and throws marble straight downward toward the sidewalk below at a speed of 5.00 m/s and the window is 39.0 meters above the sidewalk. Answer the two questions below, using three significant digits.

The volume of a block of iron is 9 cc and its mass is 70.83 g. what would be the volume of a block of aluminum that has the same mass as the block of iron? (the density of aluminum is 2.70 g/cc)

A 1000 kg satellite and a 2000 kg satellite follow exactly the same orbit around the earth. What is the ratio F1/F2 of the gravitational force on the first satellite to that on the second satellite?

How does the skater's kinetic energy changes as he moves down the ramp?

A 50.0kg bicyclist on a 10.0kg bicycle speeds up from a 5.00m/s to 10.0m/s

How tightly does mass need to be compacted in order to become a black hole? (2 words)

2NaClO = 2NaCl + O2 what kind of reaction is happening