A mass of 5 kg sits at rest on an incline making an angle of 30° to the horizontal. If ?s = 0.7, what is the friction force on the block?

2

Physics & Space Science

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The distance between one positive peak and the next positive peak of a wave is called _____

A. Frequency B. wavelength C. elasticity D. intensity

Physics & Space Science

Two blocks of masses 30.0 kg and 8.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8.0-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.60 m/s2 what is the tension in the connecting string between the blocks?

a. 23 N b. 37 N c. 18 N d. 4.8 N e. 50 N

Physics & Space Science

A particle in a rigid box has a ground state energy of 4 MeV. What is the least energy this system can absorb?

A) 16 MeV B) 4 MeV C) 25 MeV D) 12 MeV E) 8 MeV

Physics & Space Science

Astronomers have identified more and more black holes in recent years by using x-ray imaging. If black holes are supposed to be black and not emit light, where are the x rays coming from?

a. The accretion disk is full of accelerating atoms, which emit electromagnetic radiation as they accelerate. b. The friction within the accretion disk heats the gas to very high temperatures, and the gas emits x rays according to its characteristic spectrum. c. Hawking radiation not captured by the black hole knocks out K shell electrons within the accretion disk and the matter emits characteristic x rays. d. Scientists suspect that many of the supposed black holes are indeed neutron stars that emit x-ray radiation. e. Gravitational waves coming from the black hole are thought to interact with matter in the accretion disk, exciting many of the atoms into producing x rays.

Physics & Space Science