Fuses and circuit breakers are used to prevent
a. electrical shocks. b. wires overheating and causing fires.
c. save on the cost of electricity. d. to store energy.
b
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A 1.86-kg block is held in place against the spring by a 81-N horizontal external force (see the figure). The external force is removed, and the block is projected with a velocity v1 = 1.2 m/s upon separation from the spring
The block descends a ramp and has a velocity at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction over this section is 0.28. The velocity of the block is v3 = 1.4 m/s at C. The block moves on to D, where it stops. The height h of the ramp is closest to A) 11 B) 7.3 C) 15 D) 17 E) 18
A boat in a small pool is loaded with a barrel full of water. If the water in the barrel is poured overboard, into the pool, the boat will
1) sink farther into the water, 2) ride higher in the water, 3) ride no higher or lower in the water, and the water level at the side of the pool will 4) rise. 5) fall. 6) remain unchanged.
How are rotation curves of spiral galaxies determined for orbital distances beyond where starlight can be detected?
A) by extrapolation of the measured rotation curve B) by observations of the 21 cm line of atomic hydrogen C) by observations of spectral lines emitted by dark matter D) by watching the galaxies rotate over a period of decades E) by measuring the broadening of the galaxy's absorption lines
Hydrogen should be a more useful coolant than water because its specific heat is greater. Explain why this is not the case in practice
What will be an ideal response?