Physics: Homework #3 Mastel Adaptive Follow Goo e Chrome https:// mastering phys
ID: 1405887 • Letter: P
Question
Physics: Homework #3 Mastel Adaptive Follow Goo e Chrome https:// mastering physics.com pre Session PHY 1 Fall 2015 Signed in a Homework #3 Adaptive Follow-U Practice Problem 2.1 Resources em 2 next previous Practice Problem 2.1 SOLUTION SET UP As shown in (Figure 2), we choose a coordinate system Now let's apply our definition of average velocity to a swimming competition with the origin at the starting point often a convenient choice During one heat of a swi meet, a swimmer performs the crawl stroke in a pool and z increasing to the right We add the information given to the diagram we sketch for the problem m 50.0 m long, as shown in (Figure 1). She swims a length at racing speed, taking SOLVE Part (a): For the first length, we have z1 0, z2 50.0 m, t 0, and to 24.0 s. Using the definition of average 24.0 s to cover the length of the pool. She then takes twice that me to SW velocity, we find that casually back to her starting point. Find (a) her average velocity for each length and (b) her average velocity for the entire swim 50.0 m-0 m 2.08 m/s 24.0 s-0 s 50.0 m, 2 0, t 24.0 s, and to 24.0 s+ 48.00 s 72.0 s. Using the definition of For the return trip, we have z average velocity again, we obtain 0 0.0 m 1.04 m/s 72.0 24.0 s Part (b): The starting and finishing points are the same: z 22 0. Because the total displacement for a round-trip is zero, the average velocity is zero REFLECT The average z component of velocity in part (b) is negative because ac2 lies to the left of zi on the axis and 2 is decreasing during this part of the trip. Thus, the average velocity vector points to the right for part (a) and to the left for part (b) The average velocity for the total out-and-back trip is zero because the total displacement is zero Part A Practice Problem: If the swimmer could cross a 34 km channel maintaining the same average velocity as for the first 50 m in the pool, how long Figure 1 of 2 would it take? Express your answer in hours to two significant figures. m 50.0Explanation / Answer
average velocity during first 50 m = 2.08 m/s
for 34km = 34000 m ,
time taken be T ,
as velocity = distance / time
time = distance / velocity = 34000/2.08 = 16346.15 s = 272.435 minutes = 4.5 hrs