# Physics help

**Question description**

1. A boat moves at 5.00 m/s relative to the water. (You can neglect relativity at these slow speeds.)

a. Find the boat's speed relative to shore when it's traveling downstream in a river with a 3.0 current.

b. Find the boat's speed relative to shore when it's traveling upstream in a river with a 3.0 current.

c. The boat travels 100 m downstream and then 100 m upstream, returning to its original point. Find the time for the round trip. t =

2. In the future, speeding tickets for spaceships will be issued based on the spaceship's measured length. The Neptune 3000 spaceship has proper length 85 m .

a. If the posted speed limit is 0.6c , will the Neptune 3000 spaceship be ticketed if space police measure its length as 75m ? y or N?

3. An astronaut returning to Earth after a long trip is cruising earthward at 6.57×10^7m/s . She launches a package toward home, at a speed of 1.52×10^7 m/s relative to her spacecraft.

a. At what speed does the package reach Earth? v =

4. a. Find the energy of one quantum of microwave radiation with frequency 8 GHz .E1 =

b. Find the energy of one quantum of microwave radiation with frequency 100 GHz .E2 =

5. a. What's the kinetic energy of an electron having de Broglie wavelength 430nm ? K =

b. Compare with the energy of a photon having the same wavelength. E-photon/K =

6. The W+ is an elementary particle with rest energy around 80 GeV , uncertain by about 2.0 GeV .

Use Heisenberg's uncertainty principle to estimate this particle's minimum lifetime.

Change in t =

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