# Modern Physics

4. What are the strength and direction of an electric field that will balance the weight of a 1 g plastic sphere that has been charged to -3 nC?

Calculate the frame rate (in Hz) for each of the following conditions: 1. P.R.F. = 4 kHz, lines per frame = 120, 1 focal zone: 2. P.R.P. = 200 us, lines per frame = 200, 2 focal zones: 3. Max. depth = 11 cm, lines per frame = 140, 2 focal zones:

How many possible combinations are there in each system: 2 bit: 3 bit: 6 bit: 8 bit: 9 bit: 10 bit:

For each of the following, name the special feature you would use: 1. You want to decrease compression only in areas very close to a border, in order to make these borders more easily visible. 2. You want to add more scan lines to your image by sliding the transducer along the scan plane (making your picture much wider). 3. You want to change the shades of gray on your frozen picture to shades of magenta (or some other color). 4. You want the machine to automatically fill in the blank areas between diverging scan lines of your sector image with "fake" pixels. 5. You want to make your gray-scale imaging sensitive enough to pick up echoes from red blood cells as they move through the vessels. 6. You want the machine to take multiple frames and average them together in order to cancel out the random, background noise. 7. You want to enlarge a certain area of the anatomy by concentrating more scan lines in just that one selected area and filling the screen with just these lines (must be done before freezing the image). 8. Instead of seeing a 2-D picture of the anatomy, you want a graph showing the exact amplitudes or intensities of all the echoes in just one scan line.

Physics Quiz #3 Review (Chapter 4 - Part 2) 19. Which function of the machine is responsible for putting all of the scan line data together in preparation for frame (image) production? Where in the instrument does this happen?

What is the approximate size of the atom? 10-10m 10-35m 10-7m

1.3 Mass Dependance

3. A group of hikers hears an echo 4.50 s after shouting. How far away is the mountain that reflected the sound wave? (Assume the speed of sound is 347 m/s.)

5) [Work Done] A weightlifter has a basal metabolic rate of 80.0 W. As he is working out, his metabolic rate increases by about 650 W. a) How many hours does it take him to work off a 450-Calorie bagel if he stays in bed all day? b) How long does it take him if he's working out? c) Calculate the amount of mechanical work necessary to lift a 120 kg barbell 2.00m. d) He drops the barbell to the floor and lifts it repeatedly. How many times per minute must he repeat this process to do an amount of mechanical work equivalent to his metabolic rate increase of 650 W during the exercise? e) Could he actually do repetitions at the rate found in part (d) at the given metabolic level? Explain.

7. a) What is the electric field at point P? b) An electron is placed at point P, what is the resulting force on the electron (magnitude and direction)? 6 nm q=-9pC