A football game customarily begins with a coin toss to determine who kicks off. The referee tosses the coin up with an initial speed of 5.00 m/s. In the absence of air resistance, how high does the coin go above its point of release?
Reasoning
The coin is given an upward initial velocity, as in Figure 2.18. But the acceleration due to gravity points downward. Since the velocity and acceleration point in opposite directions, the coin slows down as it moves upward. Eventually, the velocity of the coin becomes v
=0 m/s at the highest point. Assuming that the upward direction is positive, the data can be summarized as shown below:
Coin Data
y
a
v
v0
t
?
–9.80 m/s2
0 m/s
+5.00 m/s
With these data, we can use Equation 2.9 (v2=v02+2ay) to find the maximum height y.
Figure 2.18
At the start of a football game, a referee tosses a coin upward with an initial velocity of v0 =+5.00 m/s. The velocity of the coin is momentarily zero when the coin reaches its maximum height.
Solution Rearranging Equation 2.9, we find that the maximum height of the coin above its release point is
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