PHYS 1401
Homework #1
1. For each of the following, tell whether nm, μm, mm, m, or km is the most appropriate unit. Explain your answer
a. The distance from
b. A sprint in track and field
c. The thickness of a piece of paper
d. The size of an atom
e. The size of a letter on this page
2. List the fundamental units in the SI system.
3. a) Describe the process for converting 15 yd to m. b) Carry out the conversion.
4. a) Explain whether you prefer to change metric prefixes by powers of 10 or conversion factors. b) Explain why. c) Carry out the following conversions i) Convert 25.4 m to km ii) Convert 1.65 km to m iii) Convert 25.4 μm to nm.
5. a) How many seconds are there in a year? b) Explain your reasoning.
6. a) Make a conversion factor from m/s to mph b) Describe a ''rule of thumb'' for converting m/s to mph.
7. a) Explain how you have to do
unit conversions which include exponents on the units. b) Convert the following
i) 25 cm3 to mm3 ii) 50 m2 to yd2
8. The wavelength of the major component of a sodium lamp is 589 nm. Convert this to inches.
9. Write a problem corresponding to the following unit conversion.
10. a) Rank the motion diagrams shown below from the lowest to the highest speed. If two diagrams have the same speed, give them the same ranking. Assume that in each diagram the dots are evenly spaced. b) Explain your reasoning.
11. a) Write a story corresponding to the graph of distance versus time shown below.
b) Sketch a graph of velocity versus time for the distance versus time graph shown.
c) Sketch a graph of position vs. time for the following situation. A car moves east at a constant speed of 20 m/s for 30s, comes to a stop for 20 s, and then heads east again at 30 m/s for 40 s.
12. Explain how the graph of distance versus time would differ for a car heading east at 30 m/s and a car heading west at 30 m/s.
13. A car travels east and covers a distance of 210 m in a time of 35 s. a) Sketch the situation. b) Find the average velocity for the car. c) Explain how you can use this information to predict how far the car will travel in 4.5 minutes. d) Find the distance traveled by the car in 4.5 minutes. e) Construct a quantitative motion diagram for the car in .5 minute intervals.
14. Below are shown two graphs of distance versus time for cars labeled 1 and 2. a) Your friend states the car 1 has the greater acceleration because the graph is steeper. Explain to your friend why he or she is wrong. b) Find the average velocity of each car. c) Find the average acceleration of each car.
15. Shown below is a motion diagram for two cars traveling in adjacent lanes on a highway. At time 4 the car 2 passes car 1. a) How do the velocities of the cars compare at this time. b) Explain your answer.
16. A car travels initially at a speed of 35 m/s. The driver steps on the brake and brings the car to a stop with a constant acceleration in a distance of 175 m. a) Sketch the situation. b) Explain how you can find the acceleration and the time it takes for the car to stop. c) Find the acceleration and the time it takes for the car to stop. d) Explain why the acceleration is negative.
17. A ball is tossed up from ground level with an initial velocity of 40 m/s. a) Sketch the situation. b) Explain how you can find the maximum height reached by the ball.
c) Find the maximum height reached by the ball. d) How long does it take for the ball to reach the maximum height? (Continued on next page)
e) At what time will the ball reach the ground again? f) What will be the speed of the ball as it reaches the ground? g) At what time will the ball reach half its maximum height? What will be the speed of the ball at that height?
18. A rubber ball is bounced on the ground and bounces up but not all the way to the height from which it was released. a) Does this motion exhibit time reversal symmetry? b) Explain your reasoning.
Problems from the text