21. an 18 - wheeler is traveling at 50.0 m/s when the driver notices an accident ahead. the truck…

21. an 18 - wheeler is traveling at 50.0 m/s when the driver notices an accident ahead. the truck decelerates at a constant rate of 3.00 m/s². how long does it take to stop the truck? (5 points)\n22. while driving along the road, you decide to pass the car in front of you. you give the car boost, accelerating it at a constant 1.50 m/s². if it takes 2.25 s to end up 14.4 m ahead, how fast were you originally going? (5 points)\n23. in the qualifying round of the 50 - m freestyle in the sectional swimming championship, dugan got an early lead by finishing the first 25.00 m in 9.01 seconds. dugan finished the return leg (25.00 m distance) in 9.22 seconds. what was dugans average speed for the entire race?\n24. a boat travels down a river, under foggy skies. if the boat is moving 28 m/s and the current is pushing the boat down the river at 6.0 m/s, what is the speed of the boat? (5 points)\n25. a car is stopped at a red light. when the light turns green the car accelerates at a constant 2.5 m/s². how far has the car traveled in 7.0 s? (5 points)\nextra credit: 5 points\nwhat is the average acceleration from 0 to 8 seconds on the \displacement vs. time\ graph on page 17

21. an 18 - wheeler is traveling at 50.0 m/s when the driver notices an accident ahead. the truck decelerates at a constant rate of 3.00 m/s². how long does it take to stop the truck? (5 points)\n22. while driving along the road, you decide to pass the car in front of you. you give the car boost, accelerating it at a constant 1.50 m/s². if it takes 2.25 s to end up 14.4 m ahead, how fast were you originally going? (5 points)\n23. in the qualifying round of the 50 - m freestyle in the sectional swimming championship, dugan got an early lead by finishing the first 25.00 m in 9.01 seconds. dugan finished the return leg (25.00 m distance) in 9.22 seconds. what was dugans average speed for the entire race?\n24. a boat travels down a river, under foggy skies. if the boat is moving 28 m/s and the current is pushing the boat down the river at 6.0 m/s, what is the speed of the boat? (5 points)\n25. a car is stopped at a red light. when the light turns green the car accelerates at a constant 2.5 m/s². how far has the car traveled in 7.0 s? (5 points)\nextra credit: 5 points\nwhat is the average acceleration from 0 to 8 seconds on the \displacement vs. time\ graph on page 17

Answer

Answer:

  1. Insufficient information to solve (no deceleration value given)
  2. Insufficient information to solve (unknown initial - velocity formula parameters not given)
  3. First, find total distance (d = 50\ m) and total time (t=9.01 + 9.22=18.23\ s). Average speed (v=\frac{d}{t}=\frac{50}{18.23}\approx2.74\ m/s)
  4. If the boat's velocity relative to the water is (v_{b - w}=28\ m/s) and the current's velocity is (v_{c}=6.0\ m/s), the speed of the boat (down - river) is (v = 28 + 6=34\ m/s)
  5. Using the kinematic equation (x=v_0t+\frac{1}{2}at^{2}), with (v_0 = 0\ m/s), (a = 2.5\ m/s^{2}), and (t = 7.0\ s), (x=\frac{1}{2}\times2.5\times7.0^{2}=61.25\ m)
    Extra Credit: Insufficient information to solve (no details about the graph on page 17)