Problem 72
As an airplane taxis on the runway with a speed of \(16.5 \mathrm{~m} / \mathrm{s}\), a flight attendant walks toward the tail of the plane with a speed of \(1.22 \mathrm{~m} / \mathrm{s}\). What is the flight attendant's speed relative to the ground?
Problem 73
As you hurry to catch your flight at the local airport, you encounter a moving walkway that is \(85 \mathrm{~m}\) long and has a speed of \(2.2 \mathrm{~m} / \mathrm{s}\) relative to the ground. If it takes you \(68 \mathrm{~s}\) to cover \(85 \mathrm{~m}\) when walking on the ground, how long will it take you to cover the same distance on the walkway? Assume that you walk with the same speed on the walkway as you do on the ground.
Problem 74
A migrating robin flies due north with a speed of \(12 \mathrm{~m} / \mathrm{s}\) relative to the air. The air moves due east with a speed of \(6.1 \mathrm{~m} / \mathrm{s}\) relative to the ground. What is the robin's speed relative to the ground?
Problem 75
A passenger walks from one side of a ferry to the other as it approaches a dock. If the passenger's velocity is \(1.50 \mathrm{~m} / \mathrm{s}\) due north relative to the ferry and \(4.50 \mathrm{~m} / \mathrm{s}\) at an angle of \(30.0^{\circ}\) west of north relative to the water, what are the direction and magnitude of the ferry's velocity relative to the water?
Problem 76
The pilot of an airplane wishes to fly due north, but there is a \(36 \mathrm{~km} / \mathrm{h}\) wind blowing toward the west. (a) In what direction should the pilot head her plane if its speed relative to the air is \(350 \mathrm{~km} / \mathrm{h}\) ? (b) Draw a vector diagram that illustrates your result in part (a). (c) If the pilot decreases the airspeed of the plane, but still wants to head due north, should she increase or decrease the angle found in part (a)?
Problem 78
The initial velocity of a projectile has a horizontal component equal to \(5 \mathrm{~m} / \mathrm{s}\) and a vertical component equal to \(6 \mathrm{~m} / \mathrm{s}\). At the highest point of the projectile's flight, what is (a) the horizontal component of its velocity and (b) the vertical component of its velocity? Explain.
Problem 79
A boy rides on a pony that is walking with constant velocity. The boy leans over to one side, and a scoop of ice cream falls from his ice cream cone. Describe the path of the scoop of ice cream as seen by (a) the child and (b) his parents standing on the ground nearby.
Problem 80
What is the acceleration of a projectile when it reaches its highest point? What is its acceleration just before and just after reaching this point?
Problem 82
A projectile is launched with an initial speed of \(12 \mathrm{~m} / \mathrm{s}\). At its highest point its speed is \(6 \mathrm{~m} / \mathrm{s}\). What was the launch angle of the projectile?
Problem 83
A racquet ball is struck in such a way that it leaves the racquet with a speed of \(4.87 \mathrm{~m} / \mathrm{s}\) in the horizontal direction. When the ball hits the court, it is a horizontal distance of \(1.95 \mathrm{~m}\) from the racquet. Find the height of the racquet ball when it left the racquet.
