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A fisherman sets out upstream on a river. His small boat, powered by an outboard motor, travels at a constant speed v in still water. The water (Urn’s at a lower constant speed vw. The fisherman has traveled upstream for 2.00 km when his ice chest falls out of the boat. He notices that the chest is missing only after he has gone upstream for another 15.0 min. At that point, he turns around and heads back downstream, all the time traveling at the same speed relative to the water. He catches up with the floating ice chest just as he returns to his starting point. How last is the river flowing? Solve this problem in two ways. (a) First, use the Earth as a reference frame. With respect to the Earth, the boat travels upstream at speed v − vw, and downstream at v + vw. (b) A second much simpler and more elegant solution is obtained by using the water as the reference frame. This approach has important applications in many more complicated problems; examples are calculating the motion of rockets and satellites and analyzing the scattering of subatomic particles from massive targets.
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Chapter 4 Solutions
PHYSICS:F/SCI.+ENGRS.,V.1
- A diver jumps off a cliff of h at an angle of 0 =38° (see figure below). He reaches a maximum height of hmaz x = 42m from the base of the cliff. Determine the speed of the diver just before he hits the water, = 3m above the top of the cliff before falling to the water below. He hits the water VA =?.Express your answer in units of m/s. Take g 9.80m/s2. Round your answer to zero decimal places. Jrmax Answer:arrow_forwardA catapult lunches a rock at a castle wall. The rock is lunched at a 45 degree angle with a speed of 22 m/s. the castle wall is 45 m away and is 20 m high. Does the rock make it over the wall?arrow_forwardIn the Marvel comic series X-Men, Colossus would sometimes throw Wolverine toward an enemy in what was called a fastball special. Suppose Colossus throws Wolverine at an angle of e = 28.1° with respect to the ground (see figure below). Wolverine is d = 2.20 m above the ground when he is released, and he leaves Colossus's hands with a speed of v. = 22.6 m/s. (a) Using conservation of energy and the components of the initial velocity, find the maximum height attained by Wolverine during the flight. (b) Using conservation of energy, what is Wolverine's speed the instant before he hits the ground? | m/sarrow_forward
- A ball of mass 1.2 kg and a diameter of 36.1 cm is attached to a string of length 1.6 m. It moves in a circular path at constant speed, 5.2 m above the ground. The string makes a constant angle of 43 ° with respect to vertical. L m (a) What is the speed of the ball? (b) What is the tension in the string?arrow_forwardA skier with a mass of 63.0 kg starts from rest and skis down an icy slope that has a length of 53.0 m at an angle of 32 degrees with respect to the horizontal. At the bottom of the slope, the path levels out and becomes horizontal, the snow becomes less icy, and the skier begins to slow down, coming to rest in a distance of 122m along the horizontal path. What is the speed of the skier at the bottom of the slope? What is the coefficient of kinetic friction between the skier and the horizontal surface?arrow_forwardIn the Marvel comic series X-Men, Colossus would sometimes throw Wolverine toward an enemy in what was called a fastball special. Suppose Colossus throws Wolverine at an angle of 8 = 33.2° with respect to the ground (see figure below). Wolverine is d = 2.17 m above the ground when he is released, and he leaves Colossus's hands with a speed of v. = 17.1 m/s. (a) Using conservation of energy and the components of the initial velocity, find the maximum height attained by Wolverine during the flight. (b) Using conservation of energy, what is Wolverine's speed the instant before he hits the ground? m/sarrow_forward
- An airplane flies horizontally at a height of h = 7840 m and with a speed of 720 km/h. A package is released from the plane which then hits the ground and explodes. Find the approximate time it takes for the package to reach the ground.Select one: a. 40sb. 20sc. 30sd. 10sarrow_forwardHello, there are several variables I have had to find for this problem but I am stuck on figuring out the last two. Please help! Thank you. A rock is thrown off a cliff at an angle of 60∘ with respect to the horizontal. The cliff is 128 m high. The initial speed of the rock is 32 m/s. Known:v0= 32 m/s v0x= 16 m/s v0y= 27.6 m/s Δy= 39.12 m t(ground)= 8.76 s Δx(total)= 138.72 m Unknown: How far has it moved horizontally when it is at maximum altitude? Δx= ? What are the horizontal and vertical positions of the rock relative to the edge of the cliff at t = 4.4 s. Assume that the origin (0,0) for this part is loacted at the edge of the cliff. Enter the positions with their correct signs. Position: (x= ? , y= ?)marrow_forwardI need help with this HW problemarrow_forward
- A physics book slides off a horizontal table top with a speed of 1.10 m/s. It strikes the floor after a time of 0.480 s. Ignore air resistance. Find the horizontal distance from the edge of the table to the point where the book strikes the floor.arrow_forwardA 4.20–kg block is set into motion up an inclined plane with an initial speed of vi = 7.60 m/s (see figure below). The block comes to rest after traveling d = 3.00 m along the plane, which is inclined at an angle of θ = 30.0° to the horizontal. An inclined plane makes an angle of θ with the horizontal. A block is shown on the plane at two different positions, a distance d apart. An arrow labeled vi is above the lower position of the block, and points up and to the right, parallel to the plane. (a) For this motion, determine the change in the block's kinetic energy.J(b) For this motion, determine the change in potential energy of the block–Earth system.J(c) Determine the friction force exerted on the block (assumed to be constant).N(d) What is the coefficient of kinetic friction?arrow_forwardA student is late for a test! She takes her motorcycle to get to school, but sees that a bridge on the way is washed out. She decides to try leaping it with her motorcycle. The side the motorcycle is on is 18.2 m above the river, whereas the opposite side is a mere 8.10 m above the river. The river itself is a raging torrent 26.0 m wide. How fast must she be going to make it safely across? Use projectile motion, and assume the initial speed is purely horizontal. Edit Format Table 12pt v Paragraph BIU A✓ ✓ T² v ⠀arrow_forward
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