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Ahat [919]
2 years ago
7

What does it mean that energy cannot be created or destroyed?

Physics
2 answers:
goldfiish [28.3K]2 years ago
8 0

Answer:

energy can only be transformed

Explanation: i took the test

dsp732 years ago
4 0

Answer:

Kinected energy cannot be transform into kinetic energy.

Explanation:

I took test

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A disk rotates about its central axis starting from rest and accelerates with constant angular acceleration. At one time it is r
atroni [7]

(a) 2.79 rev/s^2

The angular acceleration can be calculated by using the following equation:

\omega_f^2 - \omega_i^2 = 2 \alpha \theta

where:

\omega_f = 20.0 rev/s is the final angular speed

\omega_i = 11.0 rev/s is the initial angular speed

\alpha is the angular acceleration

\theta=50.0 rev is the number of revolutions made by the disk while accelerating

Solving the equation for \alpha, we find

\alpha=\frac{\omega_f^2-\omega_i^2}{2d}=\frac{(20.0 rev/s)^2-(11.0 rev/s)^2}{2(50.0 rev)}=2.79 rev/s^2

(b) 3.23 s

The time needed to complete the 50.0 revolutions can be found by using the equation:

\alpha = \frac{\omega_f-\omega_i}{t}

where

\omega_f = 20.0 rev/s is the final angular speed

\omega_i = 11.0 rev/s is the initial angular speed

\alpha=2.79 rev/s^2 is the angular acceleration

t is the time

Solving for t, we find

t=\frac{\omega_f-\omega_i}{\alpha}=\frac{20.0 rev/s-11.0 rev/s}{2.79 rev/s^2}=3.23 s

(c) 3.94 s

Assuming the disk always kept the same acceleration, then the time required to reach the 11.0 rev/s angular speed can be found again by using

\alpha = \frac{\omega_f-\omega_i}{t}

where

\omega_f = 11.0 rev/s is the final angular speed

\omega_i = 0 rev/s is the initial angular speed

\alpha=2.79 rev/s^2 is the angular acceleration

t is the time

Solving for t, we find

t=\frac{\omega_f-\omega_i}{\alpha}=\frac{11.0 rev/s-0 rev/s}{2.79 rev/s^2}=3.94 s

(d) 21.7 revolutions

The number of revolutions made by the disk to reach the 11.0 rev/s angular speed can be found by using

\omega_f^2 - \omega_i^2 = 2 \alpha \theta

where:

\omega_f = 11.0 rev/s is the final angular speed

\omega_i = 0 rev/s is the initial angular speed

\alpha=2.79 rev/s^2 is the angular acceleration

\theta=? is the number of revolutions made by the disk while accelerating

Solving the equation for \theta, we find

\theta=\frac{\omega_f^2-\omega_i^2}{2\alpha}=\frac{(11.0 rev/s)^2-0^2}{2(2.79 rev/s^2)}=21.7 rev

4 0
3 years ago
Your cell phone typically consumes about 390 mW of power when you text a friend. If the phone is operated using a lithium-ion ba
yulyashka [42]

Answer:

I = 0.11 A

Explanation:

  • In an electric circuit, the power delivered to a load, is just the product of the potential difference between the load terminals, times the current flowing through it, as follows:

       P = V*I

  • In this case, the power is the one consumed by the cell phone = 390 mW, and the voltage the one produced by the internal energy of the battery, 3.5 V, neglecting the voltage loss at the internal resistance of the battery.
  • So, we can solve the above equation for  the current I, as follows:

        I = \frac{P}{V} = \frac{0.39W}{3.5V}  = 0.11 A

  • The current flowing through the cell-phone circuitry is 0.11 A.
4 0
3 years ago
A 225 kg red bumper car is moving at 3.0 m/s. It hits a stationary 180 kg blue bumper car. The red and blue bumper cars combine
klemol [59]
I think the answer for the question above its            b 1.2
6 0
3 years ago
Read 2 more answers
Where does body heat come from?
ruslelena [56]

Friction produces heat

8 0
2 years ago
Read 2 more answers
What is the change in potential energy of a squirrel that jumps from a tree branch that is 4.5 meters off of the ground and land
quester [9]

Answer:

16.3 joules...................

3 0
3 years ago
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