/ The radius of a semicircle is increasing at the rate of 0.8 cm/s. Calculate the rate of change in the area and the perimeter of the semicircle when the radius is 5 cm

College Algebra
10th Edition
ISBN:9781337282291
Author:Ron Larson
Publisher:Ron Larson
Chapter3: Polynomial Functions
Section3.5: Mathematical Modeling And Variation
Problem 7ECP: The kinetic energy E of an object varies jointly with the object’s mass m and the square of the...
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30..answer no 1 do like example 6 solution 

TUTORIAL 30
The radius of a semicircle is increasing at the rate of 0.8 cm/s. Calculate the rate of
change in the area and the perimeter of the semicircle when the radius is 5 cm
2 A stone dropped into a still pond sends out a circular ripple whose area increases at a
rate of 5 cm'/s. How fast is the radius of the ripple changing when the radius is 2 cm ?
3 Oil from a leaking oil tanker radiates outward in the form of a circular film on the surface
of the water. If the area of the circle increases at the rate of 400 m'/min, how fast is the
radius of the circle increasing when the area is 1225n m.
4. The radius, rcm of a circle at time t is given by r = 21 + 3. Determine the rate of
change in the area when t = 1. (Give your answer in terms of n).
5. The area of a semicircle is increasing at the rate of 4n cm s'.
Calculate the rate of change in the radius of the semicircle when the radius is 5 cm.
6. Oil spilled from a ruptured tanker spreads in a circle whose radius inreases at a
constant rate of 2 cm/s. How fast is the area of the spill increasing after 5 minutes ?
1. A closed cuboid has a square base and its height is twice its base. If x is the length of
the base and x increases at a rate of 3 cm s, find the rate of change of the
surface area when x is 4 cm.
8. At what rate is the volume and surface area of a cube is changing when the side is 15
cm and each side is increasing at the rate of 0.6 cm/sec.
9. The radius of a spherical balloon increases at a rate of 0.2 cms.
How fast is the volume changing at a certain instant when its volume is 288t cm.
10. A spherical balloon is to be deflated at a rate of p cm's'. The radius of the balloon
decreases ata rate of 0.5 cms when its volume is 288t cm.
Find the value of p.
11. A boy is blowing a spherical balloon at a rate of 50 cm/s. At what rate is the radius of
the balloon changing when the radius is 10 cm.
12. The surface area of a sphere decreases at a rate of 5 m's. How fast is the radius
changing when the radius is 3 m.
13. If the radius of a sphere is increasing at the constant rate of 2 mm per sec, how fast is
the volume changing when the surface area is 8 mm ?
4.
(Hint: Vaphiere = r: Agphere = 4nr")
Answers:
dA
4( 2)
de
40
Transcribed Image Text:TUTORIAL 30 The radius of a semicircle is increasing at the rate of 0.8 cm/s. Calculate the rate of change in the area and the perimeter of the semicircle when the radius is 5 cm 2 A stone dropped into a still pond sends out a circular ripple whose area increases at a rate of 5 cm'/s. How fast is the radius of the ripple changing when the radius is 2 cm ? 3 Oil from a leaking oil tanker radiates outward in the form of a circular film on the surface of the water. If the area of the circle increases at the rate of 400 m'/min, how fast is the radius of the circle increasing when the area is 1225n m. 4. The radius, rcm of a circle at time t is given by r = 21 + 3. Determine the rate of change in the area when t = 1. (Give your answer in terms of n). 5. The area of a semicircle is increasing at the rate of 4n cm s'. Calculate the rate of change in the radius of the semicircle when the radius is 5 cm. 6. Oil spilled from a ruptured tanker spreads in a circle whose radius inreases at a constant rate of 2 cm/s. How fast is the area of the spill increasing after 5 minutes ? 1. A closed cuboid has a square base and its height is twice its base. If x is the length of the base and x increases at a rate of 3 cm s, find the rate of change of the surface area when x is 4 cm. 8. At what rate is the volume and surface area of a cube is changing when the side is 15 cm and each side is increasing at the rate of 0.6 cm/sec. 9. The radius of a spherical balloon increases at a rate of 0.2 cms. How fast is the volume changing at a certain instant when its volume is 288t cm. 10. A spherical balloon is to be deflated at a rate of p cm's'. The radius of the balloon decreases ata rate of 0.5 cms when its volume is 288t cm. Find the value of p. 11. A boy is blowing a spherical balloon at a rate of 50 cm/s. At what rate is the radius of the balloon changing when the radius is 10 cm. 12. The surface area of a sphere decreases at a rate of 5 m's. How fast is the radius changing when the radius is 3 m. 13. If the radius of a sphere is increasing at the constant rate of 2 mm per sec, how fast is the volume changing when the surface area is 8 mm ? 4. (Hint: Vaphiere = r: Agphere = 4nr") Answers: dA 4( 2) de 40
Example 6:
A cuboid metal slab has a width of x m, length 2x m and height 2 m.
2 m
2x m
When heated, the widih expanded at the rate of 0.01 mh.
Find the rate of change of the surface area when the volume is 36 m,
Solution:
dA
dx
= 0.01.
dt
= ?, V = 36
dt
V =
4x
4x =
36
x =
2 ( 2x + 4x + 2x)
4x + 12x
A
%3D
dA
dx
dA
%3D
dt
dt
dx
0.01 x (8x + 12)
%3!
0.01 x (8(3) + 12)
0.36 m2 h
%3D
Alternative Solution:
A =
4x + 12x
dA
dt
dx
dx
+ 12
dt
8x
%3D
dt
8(3)(0.01) + 12 (0.01)
0.36 m h
Transcribed Image Text:Example 6: A cuboid metal slab has a width of x m, length 2x m and height 2 m. 2 m 2x m When heated, the widih expanded at the rate of 0.01 mh. Find the rate of change of the surface area when the volume is 36 m, Solution: dA dx = 0.01. dt = ?, V = 36 dt V = 4x 4x = 36 x = 2 ( 2x + 4x + 2x) 4x + 12x A %3D dA dx dA %3D dt dt dx 0.01 x (8x + 12) %3! 0.01 x (8(3) + 12) 0.36 m2 h %3D Alternative Solution: A = 4x + 12x dA dt dx dx + 12 dt 8x %3D dt 8(3)(0.01) + 12 (0.01) 0.36 m h
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