In western movies you often see a person putting his ear against the rails in the train tracks to find out if a train is approaching. Why would this give him advance knowledge of the approach of a train?
What will be an ideal response?
The speed of sound in metals is considerably faster than the speed of sound in air.
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A firecracker explodes in midair and breaks up into many fragments. Which of the following statements are true regarding conditions immediately before and immediately after the explosion: I
The total momentum of the fragments is equal to the original momentum of the firecracker. II. The total kinetic energy of the fragments is equal to the original kinetic energy of the firecracker. A) Statement I only B) Statement II only C) Both Statement I and Statement II D) Neither statement is true.
What do we mean when we say that electron energy levels in atoms are quantized?
What will be an ideal response?
An object at rest near the surface of a distant planet starts to fall freely. If the acceleration there is twice that of the Earth, its speed one second later would be
A) 10 m/s. B) 20 m/s. C) 30 m/s. D) 40 m/s.
Water is being sprayed from a nozzle at the end of a garden hose of diameter 2.0 cm. If the nozzle has an opening of diameter 0.50 cm, and if the water leaves the nozzle at a speed of 15 m/s, what is the speed of the water inside the hose?
a. 0.63 m/s c. 2.5 m/s b. 0.94 m/s d. also 10 m/s