Physics for Scientists & Engineers & Modern Physics, 9th Ed

17
that of Uranus is 1.19. The ratio of the radius of Nep-
tune to that of Uranus is 0.969. Find the average den-
sity of Neptune.
 43. Review. The ratio of the number of sparrows visiting a 
bird feeder to the number of more interesting birds is 
2.25. On a morning when altogether 91 birds visit the 
feeder, what is the number of sparrows?
 44. Review. Find every angle u between 0 and 360° for 
which the ratio of sin u to cos u is 23.00.
 45. Review. For the right tri-
angle shown in Figure 
P1.45, what are (a) the 
length of the unknown 
side, (b) the tangent of u, 
and (c) the sine of f?
 46. Review. Prove that one 
solution of the equation
2.00x
4
2 3.00x
3
1 5.00x 5 70.0

is x 5 22.22.

 47. Review. A pet lamb grows rapidly, with its mass pro-
portional to the cube of its length. When the lamb’s 
length changes by 15.8%, its mass increases by 17.3 kg. 
Find the lamb’s mass at the end of this process.
 48. Review. A highway curve forms a section of a circle. A 
car goes around the curve as shown in the helicopter 
view of Figure P1.48. Its dashboard compass shows that 
the car is initially heading due east. After it travels d 5 
840 m, it is heading u 5 35.0° south of east. Find the 
radius of curvature of its path. Suggestion: You may find 
it useful to learn a geometric theorem stated in Appen-
dix B.3.
 
E
N
S
W
d
u
Figure P1.48
49. Review. From the set of equations
p 5 3q
pr 5 qs
1
2
pr
2
1
1
2
qs
2
5
1
2
qt
2

involving the unknowns p, q, r, s, and t, find the value 

of the ratio of t to r.