Robin Hood shoots a pear
the sound of horn, shown in Figure 3.19, Robin Hood aims directly at the toward it. His rivals
In a festival competition, a he is to shoot his arrow, and at the same instant the pear initial position of the pear, seem-
the great archer Robin Hood is challenged to hit a falling will be pear dropped with an from arrow. the top At
of a tall making tower. no As allowance for the fact that the pear is dropping Show as the that arrow if the moves arrow is aimed directly
ingly assume that this is a mistake, the but it to will their always shock, hit he the hits pear, the regardless pear. of the pear's initial location or initial
the speed initial (assuming position that neither pear nor arrow hits the ground first).
Line of sight to pear
Path of pear
Does the arrow
Notice that =
hit the pear?
Trajectory of arrow
FIGURE 3.19 Robin Hood's shot.
Kicking a field goal
For a field goal attempt, a football is kicked from a point on the
ground that is a horizontal distance S from the goalpost. For the
attempt to be successful, the ball must clear the crossbar, 10 ft
(about 3.05 m) above the ground, as shown in Figure 3.18.
The ball leaves the kicker's foot with an initial speed of
20.0 m/s at an angle of 30° above the horizontal. What is the dis-
tance d between kicker and goalpost if the ball barely clears the
The ball can pass over the goalposts on the way upor of
on the way down, so there are two possible values 1.
A FIGURE 3.18 Kicking a field goal.
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