Keep the speeds in units of c (e. g., v = 0.850c), distances in ly (light-years), time in yr (years), and never substitute a numerical value for c. keep in mind that the speed of light, in these units, is c = 1 ly/yr (one light-year per year). for constant speeds within any reference frame, speed = distance/time. imagine a star 76 ly from earth, and a probe traveling there at a speed of 0.930c a) how long will the journey from the earth to the star take, in earth's reference frame and in the probe's reference frame? b) using a faster probe would obviously cut down the journey time in both reference frames. however it isn't possible to cut the journey time in half in earth's reference frame. why not? words and numbers c) calculate the time the journey will take in the probe's reference frame if its speed is increased to 0.981c, and verify that this would cut its journey's time in half.

Around faucet handle is part of a(n) a. lever b. screw c. inclined plane d. wheel and axle

Aheat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. the same engine running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. heat pumps are widely used for home heating. you can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat qh, warming the indoors. perhaps this seems a little silly, but consider the following. electricity can be directly used to heat a home by passing an electric current through a heating coil. this is a direct, 100% conversion of work to heat. that is, 19.0 \rm kw of electric power (generated by doing work at the rate 19.0 kj/s at the power plant) produces heat energy inside the home at a rate of 19.0 kj/s. suppose that the neighbor's home has a heat pump with a coefficient of performance of 4.00, a realistic value. note: with a refrigerator, "what you get" is heat removed. but with a heat pump, "what you get" is heat delivered. so the coefficient of performance of a heat pump is k=qh/win. an average price for electricity is about 40 mj per dollar. a furnace or heat pump will run typically 200 hours per month during the winter. what does one month's heating cost in the home with a 16.0 kw electric heater? what does one month's heating cost in the home of a neighbor who uses a heat pump to provide the same amount of heating?

What does si stand for,when referring to a system of measurement