Predict/Calculate To decide who pays for lunch, a passenger on a moving train tosses a coin straight upward with an initial speed of 5.25 m/s and catches it again when it returns to its initial level. From the point of view of the passenger then, the coin’s initial velocity is (5.25 m/s) y ⌢ . The train’s velocity relative to the ground is (12.1m/s) x ⌢ . (a) What is the minimum speed of the coin relative to the ground during its flight? At what point in the coin s flight does this minimum speed occur? Explain. (b) Find the initial speed and direction of the coin as seen by an observer on the ground. (c) Use the expression for y max derived in Example 4-14 to calculate the maximum height of the coin, as seen by an observer on the ground. (d) What is the maximum height of the coin from the point of view of the passenger, who sees only one-dimensional motion?
Predict/Calculate To decide who pays for lunch, a passenger on a moving train tosses a coin straight upward with an initial speed of 5.25 m/s and catches it again when it returns to its initial level. From the point of view of the passenger then, the coin’s initial velocity is (5.25 m/s) y ⌢ . The train’s velocity relative to the ground is (12.1m/s) x ⌢ . (a) What is the minimum speed of the coin relative to the ground during its flight? At what point in the coin s flight does this minimum speed occur? Explain. (b) Find the initial speed and direction of the coin as seen by an observer on the ground. (c) Use the expression for y max derived in Example 4-14 to calculate the maximum height of the coin, as seen by an observer on the ground. (d) What is the maximum height of the coin from the point of view of the passenger, who sees only one-dimensional motion?
Predict/Calculate To decide who pays for lunch, a passenger on a moving train tosses a coin straight upward with an initial speed of 5.25 m/s and catches it again when it returns to its initial level. From the point of view of the passenger then, the coin’s initial velocity is (5.25 m/s)
y
⌢
. The train’s velocity relative to the ground is (12.1m/s)
x
⌢
. (a) What is the minimum speed of the coin relative to the ground during its flight? At what point in the coin s flight does this minimum speed occur? Explain. (b) Find the initial speed and direction of the coin as seen by an observer on the ground. (c) Use the expression for ymax derived in Example 4-14 to calculate the maximum height of the coin, as seen by an observer on the ground. (d) What is the maximum height of the coin from the point of view of the passenger, who sees only one-dimensional motion?
69) A rescue helicopter is hovering over a person whose boat has sunk. One of the rescuers throws a life preserver straight down to the victim with an initial velocity of 1.40 m/s and observes that it takes 1.8 s to reach the water. (a) List the knowns in this problem. (b) How high above the water was the preserver released? Note that the downdraft of the helicopter reduces the effects of air resistance on the falling life preserver, so that an acceleration equal to that of gravity is reasonable.
71. ssm Multiple-Concept Example 4 provides useful background for
this problem. A diver runs horizontally with a speed of 1.20 m/s off a
platform that is 10.0 m above the water. What is his speed just before
striking the water?
Problem 8. A fast duck is flying 20i + 40j Įmi/h at the same altitude as a
slow airplane flying with a velocity of ( -80i + 40j
mi/h. How fast and in what
direction is the duck moving relative to the airplane?
a) 100 mi/h, along +î
b) 100 mi/h, along -î
c) 150 mi/h, along +j
d) 150 mi/h, along -ĵ
e) 200 mi/h, along +î
Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
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