Physics

Vandebilt Catholic High School

W. Dupre

Assignment: Velocity Problems

 

Regular and Level 1:

 

  1. A walker and a runner leave your front door at the same time. They move in the same direction at different constant velocities. Sketch the position-time graphs of each (Place both the walker and the runner on the same graph).
  2. Sketch a position-time graph of a person who walks one block at a moderate speed, waits a short time for a “walk” light, walks the next block more slowly, then the final block very fast. All blocks are of equal length.
  3. A NASA team oversees a space shuttle launch at Cape Canaveral in Florida and then travels to Edwards Air Force Base in California to supervise the landing. Which group of people, the astronauts or the NASA team, has the greater displacement?
  4. If the average velocity of a particle is zero in some time interval, what can you say about its displacement for that interval?
  5. Use the intervals marked on the graph in Figure 3-20b to describe the velocity of the object during each interval.

 

 

 

 

Regular Class Only:

 

  1. A person walks 3 km in 2.0 h. What is the person’s average velocity in km/h and m/s?

                              Table 3-1

Clock Readings (t)

 in seconds (s)

Positions (d),

 in meters (m)

0.0

0.0

1.0

2.0

2.0

8.0

3.0

18.0

4.0

32.9

5.0

50.0

 

  1. The total distance a steel ball rolls down an incline at various times is given in Table 3-1. (a) Draw a position-time graph of the motion of the ball. When setting up the axes, use five divisions for each 10 m of travel on the d-axis. Use five divisions for each second of time on the t-axis. (b) What type of curve is the line of the graph? (c) What distance has the ball rolled at the end of 2.2 s?
  2. A train leaves the station at the 0.0-m marker traveling with a constant velocity of 36.0 m/s.

      a. How many seconds later will the train pass the 1620.0-m marker?

  1. At l :00 PM, a car, traveling at a constant velocity of 94 km/h toward the west, is 17 km to the west of your school. Where will it be at3:30 PM?
  2. Suppose the car in Problem 10 started 17 km east of your school at the same time, moving in the same direction at the same velocity.

      a. Where would it be at 3:30 PM

      b. When would it be at your school?

  1. While John is traveling along a straight inter state highway, he notices that the mile marker reads 260. John travels until he reaches the150-mile marker and then retraces his path to the 175-mile marker. What is John resultant displacement from the 260-mile marker?
  2. Light from the sun reaches Earth in 8.3 m The velocity of light is 3.00 x 1008 m/s. How far is Earth from the sun?
  3. Ann is driving down a Street at 55 km/h. Suddenly a child runs into the street. If it takes Ann 0.75 s to react and apply the brakes, how many meters will she have moved before she begins to slow down?
  4. You drive a car 2.0 h at 40 km/h then 2.0 at 60 km/h. a) What is your average velocity? b) Do you get the same answer if you drive 100 km at each of the two speeds above?
  5.   Both car A and car B leave school when a clock reads zero. Car A travels at a constant 75 km/h while car B travels at 85 km/h. a) Draw a position-time graph showing the motion of both cars. How far are the two cars from school when the clock reads 2.0 h? Calculate the distances using the equation of motion and show them on your graph. Both cars passed a gas station 100 km from the school. When did each car pass the station? Calculate the times and show them on your graph.

 

 

 

Level 1 Classes Only:

 

  1. You plan a trip on which you want to average 90 km/h. You cover the first half of the distance at an average speed of only 48 km/h. What must your average speed be in the second half of the trip to meet your goal? Note that the velocities are based on half the distance, not half the time.
  2. Draw a position-time graph for two cars driving to the beach, 50 km from school. Car A leaves a store 10 km from school closer to the beach at noon, and drives at 40 km/h. Car B starts from school at 12:30 P.M and drives at 100 km/h. When does each get to the beach?
  3. Two cars travel along a straight road. When a stopwatch reads t = 0.00 h, car A is at da = 48.0 km moving at a constant 36.0 km/h. Later, when the watch reads t = 0.50 h, car B is at db = 0.00 km moving at 48.0 km/h. a) What will the watch read when car B passes car A? b) At what position will the passing occur? c) When the cars pass, how long will it have been since car A was at the reference point?
  4. The position of a pine wood derby car was observed at various times and the results are summarized in the table below. Find the average velocity of the car for (a) the first second. (b) the last 3 seconds, and (c) the entire period of observation.

                  x (m)    0          2.3       9.2       20.7     36.8     57.5

                  t (s)      0          1.0       2.0       3.0       4.0       5.0

  1. A motorist drives north for 35 minutes at 85km/h and then stops for 15 minutes. He then continues north, traveling 130 km in 2 h. (a) What is his total displacement? (b) What is his average velocity?
  2. An athlete swims the length of a 50-m pool in 20 s and makes the return trip to the starting position in 22 s. Determine his average velocity in (a) the first half of the swim, (b) the second half of the swim, and (c) the round trip.
  3. The position of a particle along the x axis is given by = 3t3 - 7t where x is in meters and t is in seconds. What is the average velocity of the particle during the interval from t = 2.0 s tot = 5.0 s?
  4. A car makes a 200-km trip at an average speed of 40 km/h. A second car starting 1 h later arrives at their mutual destination at the same time. What was the average speed of the second car?
  5. The displacement of a body (in m) as a function of time (in s) is x = 5 + 4t – 3t2. What are the instantaneous velocities at (a) t = 0? (b) t = 0.1? (c) 2.3 s?
  6. In driving in a straight line from New York to Boston, your position function given in miles from New York is described by the function: F(x) = 5/3 t3 – 25t2 + 120 t, where t is the number of hours since the trip began. It takes you 8 hours to get to Boston. Find your velocity at time t = 1/2 hrs.
  7. Ever since you started your physics class you've suffered from blinding headaches. Nothing helps. Acupuncture, drugs, counseling, you've tried them all, but the headaches get worse and worse. The pain is unbearable, and you decide to end it all. You drive to the middle of the Golden Gate Bridge and climb over the safety rail, 400 feet above the water. With that pain, life is not worth living, so you fling your physics text (which you carry everywhere) over the edge, and jump out after it. Your height in feet over the water after t seconds is given by the function d(t) = 400 - 16t2. a) How long till you hit the water?  (b) Right after you let go of the textbook your headache disappears. You realize that it is that hated text that has been the cause of all your pain. Suddenly life is a realm of wonder, calling for your presence. You had lots of diving lessons when you were a kid. If you are traveling with a velocity of less than 200 feet per second, you can survive the plunge. Will you survive?
  8. An oil tank is to be drained for cleaning. There are V gallons of oil left in the tank after t minutes of draining, where V = 50(40 - t)2. What is the rate at which oil is flowing out of the tank 20 minutes after draining begins?