thursday
21. Calculate the magnitude of the resultant of a pair of 100-km/h velocity vectors that are at right angles to each other.
100 sq+100 sq=141
39. A boat is rowed at 8km/h directly across a river that flows at 6km/h a. What is the resultant speed of the boat?
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41. Harry accidentally falls out of a helicopter that is traveling at 100 m/s. he plunges into a swimming pool 2 seconds later. Assuming no air resistance, what was the horizontal distance between Harry and the swimming pool when he fell from the helicopter?
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44. The boy on the tower in the figure below throws a ball a distance of 60m, as shown. At what speed, in m/s, the ball thrown?
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b. How fast and in what direction can the boat be rowed to reach a destination directly across the river?
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22. Calculate the magnitude of the horizontal and vertical components of a vector that is 100 units long and oriented at 45 degrees
2xsq=100sq,x=70.1 both horizontally and vertically, 141
28. Satellites in circular, low Earth-orbit move at 8km/s. Convert this speed to miles per hour.(There are about 1.6km in 1 mile and 3600s in 1h.)
8km/1sec*3600sec/1hour*=28800km/1 hour
32.Rain falling vertically will make vertical streaks on a car's side window. However, if the car is moving, the streaks are slanted. If the streaks, how fast is the car moving compared with the speed of the falling rain?
Rain falling vertically will leave vertical streaks when the car is still.
30. If you swim in a direction directly across a river and you end up downstream due to the flow of water, do you move faster than you would if the water didn't flow? Explain.
The speed of your motion is not affected by the river because the motion of the water is 90 degrees from your motion.
31.The speed of falling rain is the same 10m above the ground as it is just before it hits the ground. What does this tell you about whether or not the rain encounters air resistance?
The rain drops are affected by a force opposing gravity, which supposedly is air resistance.
33. You're driving behind a car and wish to pass, so you turn left and pull into the passing lane without changing speed. Why does the distance increase between you and the car you're following?
cos(10)=x/v .9848=x/v x=.9848v
20. Calculate the resultant of the pair of velocities 100km/h north and 75 km/h south. Calculate the resultant if both of the velocities are directed north.
north 100+-75=25, 100+75=175 north, the difference is the second vector.
19. Calculate the resultant velocity of an airplane that normally flies at 200 km/h if it encounters a 50-km/h tailwind a 50-km/h. If it encounters a 50km/h headwind.
resultant=v1+v2, 200+50=250 m/s, tailwind 150m/s