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Ad libitum [116K]
3 years ago
12

If a system is isolated the total energy within that system is constant. Consider the case of a hot cup of coffee: when it cools

down, the energy goes into the surrounding air, causing the air to warm. If the coffee and the air are placed in an isolated chamber, the total energy of the system (coffee + air) is constant because the energy lost by the coffee is exactly equal to the energy gained by the air. The only way for the total energy of a system to change is when it is not isolated, meaning that external forces or sources of energy interact with the system. If we want to define a system where the total energy is conserved, which one of the choices below would be the best system to consider?A. The personB. The person and the EarthC. The Earth
Physics
1 answer:
uranmaximum [27]3 years ago
5 0

Answer:b-The person and the earth

Explanation:

The best system will be the person and earth as a system

It is so because whatever the energy required by the person is derived from earth resource and thus by depleting the earth resource person is getting is required form of energy .

for example person want thermal energy , for this he need coal which is earth resource and thus all the energy is derived from earth and is being converted into some other form of energy.

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A stone was dropped off a cliff and hit the ground with a speed of 88 ft/s. What is the height (in feet) of the cliff
igor_vitrenko [27]

Answer:

the height (in feet) of the cliff is 121 ft

Explanation:

A stone hit the cliff with

speed, v = 88 ft/s

Acceleration, a= 32 ft/s^2

initial speed, u = 0 ft/s

height is h.

To solve this problem we will apply the linear motion kinematic equations, Equation of motion describes change in velocity, depending on the acceleration and the distance traveled

so, writing the formula of Equation of motion:

v^2 - u^2 = 2*a*h

substituting the appropriate values,

(88)^2 - 0 = 2*32* h

h=(88)^2 / 64

h= 121 ft

hence

the height (in feet) of the cliff is 121 ft

learn more about height of the cliff here:

<u>brainly.com/question/24130198</u>

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3 0
1 year ago
b. A string is wrapped around a pulley of radius 0.05 m and moment of inertia 0.2 kg  m2. If the string is pulled with a force
Oduvanchick [21]

Answer:

f = 8 N

Explanation:

Data provided in the question

Radius of the pulley  = r = 0.05 m

Moment of inertia = (I) = 0.2 kg.m^{2}

Angular acceleration = ∝ = 2 rad/sec

Based on the above information

As we know that

Torque is

= force \times  radius

= f \times r

And,

Torque is also

= moment\ of\ inertia \times angular\ acceleration

= I \times \alpha

So,

We can say that

f \times r = I \times \alpha

f \times 0.05 = 0.2 \times 2

0.05f = 0.4

f = 8 N

We simply applied the above formulas

8 0
3 years ago
If pressure is increased from 200 kPa to 300 kPa, and the original volume of gas was 1.5 L, what is the new volume? Assume the t
Oxana [17]

Answer:

The answer to your question is:      V2 = 1 l

Explanation:

Data

P1 = 200 kPa

P2 = 300 kPa

V1 = 1.5 l

V2 = ?

Formula

                          P1V1 = P2V2

                          V2 = (P1V1) / P2

                          V2 = (200 x 1.5) / 300

                          V2 = 1 l

6 0
3 years ago
Potassium ions (K+) move across a 7.0 -mm- thick cell membrane from the inside to the outside. The potential inside the cell is
Reil [10]

Explanation:

Relation between potential energy and charge is as follows.

           U = qV

or,    \Delta U = q \times \Delta V

                   = 1.6 \times 10^{-19} \times 70 \times 10^{-3}

                   = 112 \times 10^{-22} J

or,                = 1.12 \times 10^{20} J

Therefore, we can conclude that change in the electrical potential energy \Delta U is 1.12 \times 10^{20} J.

7 0
3 years ago
A gardener mows a lawn with an old-fashioned push mower. The handle of the mower makes an angle of 320 with the surface of the l
Virty [35]

Answer:

N = 337.96 N

Explanation:

∅ = 32º

F = 249 N

m = 21 Kg

N = ?

We can apply:

∑ F = 0  (↑)

- Fy - W + N = 0   ⇒    N = Fy + W

⇒  F*Sin ∅ + m*g = N

⇒  N = (249 N*Sin32º) + (21 Kg*9.81 m/s²)

⇒  N = 337.96 N  (↑)

8 0
3 years ago
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