A football is thrown toward a receiver with
an initial speed of 15.4 m/s at an angle of
38.7
◦
above the horizontal. At that instant,
the receiver is 17.7 m from the quarterback.
The acceleration of gravity is 9.81 m/s
2
.
With what constant speed should the receiver run to catch the football at the level at
which it was thrown?
Answer in units of m/s
d=17.7 m
vₒ =15.4 m/s
α =38.7⁰ =>2 α =77.4⁰
L=vₒ²•sin2α/g=15.4²•sin77.4/9.8 =23.6 m
t= 2vₒ•sinα/g=2•15.4•sin38.7/9.8 = 1.97 s.
s=(L-d)/t =(23.6-17.7)/1.97 =3 m/s