Why is combustion of fuel necessary for heat engines to do work?

A hiker determines the length of a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.9 s after shouting. The speed of sound in air is 343 m/s. Determine the length of the lake.

A heavy piece of hanging sculpture is suspended by a 90 cm-long, 5.0 g steel wire. When the wind blows hard, the wire hums at its fundamental frequency of 80 Hz. What is the mass of the sculpture?

Which of the following is true about elements? A. Atoms of all elements contain the same number of protons, but the number of neutrons is different for every element. B. Atoms of all elements contain neutrons, but they do not all contain protons. C.

When a block of ice at zero degrees Celsius melts, the ice A) absorbs energy from its environment. B) releases energy to its environment. C) absorbs energy and gets warmer. D) releases energy and gets warmer.

If the primary of a transformer were connected to a dc power source, A. the transformer would have a voltage output the same as its input. B. at a higher efficiency than with an ac source. C. that is also dc. D.

Inside a stereo speaker, you will find two permanent magnets: one on the cone and one near the cone. True of false?

When a hurricane nears land what causes the most damage

Calculate if an electric hair dryer uses 2,400 j of energy in 2 s, what is its power?

Which of the following choices best represents a potential stressor?

How do you distinguish between speed, velocity, and acceleration?