1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Evgesh-ka [11]
3 years ago
10

An object is placed in a room where the temperature is 20 degrees C. The temperature of the object drops by 5 degrees C in 4 min

utes and by 7 degrees C in 8 minutes. What was the temperature of the object when it was initially placed in the room
Physics
1 answer:
navik [9.2K]3 years ago
8 0

Answer:

28.3°C

Explanation:

Using

T(t) = (T(0) - 20)*(e^(-k*t)) + 20

for some positive number k, and some initial temperature T(0).

Boundary conditions:

T(4) = T(0) - 5 _______ (i)

T(8) = T(0) - 7 _______ (ii)

==> solving for T(0) and k :

(i):

(T(0) - 20)*(e^(-k*4)) + 20 = T(0) - 5 ==>

(T(0) - 20)*(e^(-k*4)) = T(0) - 20 - 5

(T(0) - 20)*(e^(-k*4)) = (T(0) - 20) - 5

5 = (T(0) - 20) - (T(0) - 20)*(e^(-k*4))

5 = (T(0) - 20) * ( 1 - e^(-k*4) )

(ii):

(T(0) - 20)*(e^(-k*8)) + 20 = T(0) - 7

(T(0) - 20)*(e^(-k*8)) = (T(0) - 20) - 7

7 = (T(0) - 20) - (T(0) - 20)*(e^(-k*8))

7 = (T(0) - 20) * (1 - e^(-k*8))

In both results, subsitute x = e^(-4k) and C = (T(0) - 20)

(i): 5 = C * (1 - x)

(ii): 7 = C * (1 - x^2) = C * (1-x)*(1+x)

Substitute C*(1-x) from (i) into (ii):

(ii): 7 = 5*(1+x) ==> (1+x) = 7/5 ==> x = 2/5

back into (i):

(i): 5 = C * (1 - 2/5) ==> 5 = C * 3/5 ==> C = 25/3

C = T(0) - 20 ==>

T(0) = C + 20 = 25/3 + 20 = 25/3 + 60/3 = 85/3

= 28.3°C

You might be interested in
Block m1 of mass 2m and velocity v0 is traveling to the right (+x) and makes an elastic head-on collision with block m2 of mass
Oksana_A [137]
1) In any collision the momentum is conserved

(2*m)*(vo) + (m)*(-2*vo) = (2*m)(v1') + (m)(v2')

candel all the m factors (because they appear in all the terms on both sides of the equation)

2(vo) - 2(vo) = 2(v1') + (v2') => 2(v1') + v(2') = 0 => (v2') = - 2(v1')

2) Elastic collision => conservation of energy

=> [1/2] (2*m) (vo)^2 + [1/2](m)*(2*vo)^2 = [1/2](2*m)(v1')^2 + [1/2](m)(v2')^2

cancel all the 1/2 and m factors =>

2(vo)^2 + 4(vo)^2 = 2(v1')^2 + (v2')^2 =>

4(vo)^2 = 2(v1')^2 + (v2')^2

now replace (v2') = -2(v1')

=> 4(vo)^2 = 2(v1')^2 + [-2(v1')]^2 = 2(v1')^2 + 4(v1')^2 = 6(v1')^2 =>

(v1')^2 = [4/6] (vo)^2 =>

(v1')^2 = [2/3] (vo)^2 =>

(v1') = [√(2/3)]*(vo)

Answer: (v1') = [√(2/3)]*(vo)




 
4 0
3 years ago
Substance A has a higher heat capacity than does substance B, and substance B has a higher heat capacity than does substance C.
LekaFEV [45]
BABC that what I Think
6 0
4 years ago
A ship maneuvers to within 2500 m of an island's 1800 m high mountain peak and fires a projectile at an enemy ship 610 m on the
Ne4ueva [31]
Thank you for posting your question here at brainly. I hope the answer will help you. Feel free to ask more questions.

t=(0-(250sin75)^2)/-9.8 
<span>the distance one is (2500+610)- (250m/s*cos75)*t=Dh Dh=horizontal distance </span>

<span>the max height one is d=0.5*9.8*t^2 </span>
<span>d= max height subtract 1800-d</span>
3 0
3 years ago
Read 2 more answers
A Ferris wheel with radius 14.0 m is turning about a horizontal axis through its center. The linear speed of a passenger on the
Marina86 [1]

Answer:

a) The acceleration experimented by the passenger when she passes through the lowest point of her circular motion is: a_{R} = 2.571\,\frac{m}{s^{2}}, \angle = 90^{\circ}.

b) Hence, the acceleration experimented by the passenger when she passes through the highest point of her circular motion is: a_{R} = 2.571\,\frac{m}{s^{2}}, \angle = 270^{\circ}.

c) The Ferris wheel takes 14.646 seconds to make a revolution.

Explanation:

a) An object that rotates at constant angular velocity reports a centripetal acceleration and no tangential acceleration. When passenger passes through the lowest point in her circular motion, centripetal acceleration goes up to the center.

In addition, centripetal acceleration is determined by the following expression:

a_{R} = \frac{v^{2}}{R} (Eq. 1)

Where:

a_{R} - Centripetal acceleration, measured in meters per square second.

v - Linear speed, measured in meters per second.

R - Radius of the Ferris wheel, measured in meters.

If we know that v = 6\,\frac{m}{s} and R = 14\,m, the magnitude of radial acceleration is:

a_{R} = \frac{\left(6\,\frac{m}{s} \right)^{2}}{14\,m}

a_{R} = 2.571\,\frac{m}{s^{2}}

The acceleration experimented by the passenger when she passes through the lowest point of her circular motion is: a_{R} = 2.571\,\frac{m}{s^{2}}, \angle = 90^{\circ}.

b) In the highest point the magnitude of radial acceleration is the same but direction is the opposed to that at lowest point. That is, centripetal acceleration goes down to the center.

Hence, the acceleration experimented by the passenger when she passes through the highest point of her circular motion is: a_{R} = 2.571\,\frac{m}{s^{2}}, \angle = 270^{\circ}.

c) At first we need to calculate the angular velocity of the Ferris wheel (\omega), measured in radians per second, by using the following expression:

\omega = \frac{v}{R} (Eq. 2)

If we know that v = 6\,\frac{m}{s} and R = 14\,m, then the angular velocity of the Ferris wheel is:

\omega = \frac{6\,\frac{m}{s} }{14\,m}

\omega = 0.429\,\frac{rad}{s}

Now we proceed to obtain the period of the Ferris wheel (T), measured in seconds, which is the time needed by that wheel to make on revolution:

T = \frac{2\pi}{\omega} (Eq. 3)

Where \omega is the angular velocity of the Ferris wheel, measured in radians per second.

If we get that \omega = 0.429\,\frac{rad}{s}, then:

T = \frac{2\pi}{0.429\,\frac{rad}{s} }

T = 14.646\,s

The Ferris wheel takes 14.646 seconds to make a revolution.

8 0
3 years ago
a grocery sore just receive a shipment of 212 carton eggs each carton holds one dozen eggs if 12 eggs =1 dozen how many eggs did
Leviafan [203]
You multiply 212 by 12 to get an answer. The answer is 2,544
6 0
3 years ago
Other questions:
  • WHAT ARE THE BENEFITS OF CARDIOVASCULAR ACTIVITIES?
    5·2 answers
  • A charge of 3.20 μC is held fixed at the origin. A second charge of 3.20 μC is released from rest at the position (1.25 m, 0.570
    14·1 answer
  • 1. For each situation, determine the net force acting upon the object.
    14·1 answer
  • You can loose your flexibility?<br> True or false?
    12·1 answer
  • What happens to the gravitational force between two object if the mass of the objects stay the same but distance decreases?
    11·1 answer
  • A horse pulls a cart along a flat road. Consider the following four forces that arise in this situation. (1) the force of the ho
    5·1 answer
  • How does gravity influence our annual calendar?
    10·2 answers
  • Kate gathered 3 of the same size made of different materials: glas, clear plastic, and aluminum painted black. She placed on the
    12·1 answer
  • A wire with mass 50 g is stretched so that it’s ends are tied down at points 100 cm apart. The wire vibrates in its fundamental
    9·2 answers
  • If the radius increased between the two objects what would happen to gravitational force between them?
    14·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!