Power = (energy) / (time)
= (1370 joules) / (100 seconds)
= 13.7 joules/second
= 13.7 watts .
That's not an awful lot of power, especially for a strenuous activity like
rock-climbing. Shoot ! Even I could probably perform at that level.
Compare 13.7 watts to the light power coming out of a 20-watt night light.
13.7 watts = 0.018 horsepower. (rounded)
Answer: T is greater
Explanation:
Since the elevator is moving against gravity more work will be done on the rope
T= m(g+a)
Answer:
![V_{ft}= 317 cm/s](https://tex.z-dn.net/?f=V_%7Bft%7D%3D%20317%20cm%2Fs)
ΔK = 2.45 J
Explanation:
a) Using the law of the conservation of the linear momentum:
![P_i = P_f](https://tex.z-dn.net/?f=P_i%20%3D%20P_f)
Where:
![P_i=M_cV_{ic} + M_tV_{it}](https://tex.z-dn.net/?f=P_i%3DM_cV_%7Bic%7D%20%2B%20M_tV_%7Bit%7D)
![P_f = M_cV_{fc} + M_tV_{ft}](https://tex.z-dn.net/?f=P_f%20%3D%20M_cV_%7Bfc%7D%20%2B%20M_tV_%7Bft%7D)
Now:
![M_cV_{ic} + M_tV_{it} = M_cV_{fc} + M_tV_{ft}](https://tex.z-dn.net/?f=M_cV_%7Bic%7D%20%2B%20M_tV_%7Bit%7D%20%3D%20M_cV_%7Bfc%7D%20%2B%20M_tV_%7Bft%7D)
Where
is the mass of the car,
is the initial velocity of the car,
is the mass of train,
is the final velocity of the car and
is the final velocity of the train.
Replacing data:
![(1.1 kg)(4.95 m/s) + (3.55 kg)(2.2 m/s) = (1.1 kg)(1.8 m/s) + (3.55 kg)V_{ft}](https://tex.z-dn.net/?f=%281.1%20kg%29%284.95%20m%2Fs%29%20%2B%20%283.55%20kg%29%282.2%20m%2Fs%29%20%3D%20%281.1%20kg%29%281.8%20m%2Fs%29%20%2B%20%283.55%20kg%29V_%7Bft%7D)
Solving for
:
![V_{ft}= 3.17 m/s](https://tex.z-dn.net/?f=V_%7Bft%7D%3D%203.17%20m%2Fs)
Changed to cm/s, we get:
![V_{ft}= 3.17*100 = 317 cm/s](https://tex.z-dn.net/?f=V_%7Bft%7D%3D%203.17%2A100%20%3D%20317%20cm%2Fs)
b) The kinetic energy K is calculated as:
K = ![\frac{1}{2}MV^2](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B2%7DMV%5E2)
where M is the mass and V is the velocity.
So, the initial K is:
![K_i = \frac{1}{2}M_cV_{ic}^2+\frac{1}{2}M_tV_{it}^2](https://tex.z-dn.net/?f=K_i%20%3D%20%5Cfrac%7B1%7D%7B2%7DM_cV_%7Bic%7D%5E2%2B%5Cfrac%7B1%7D%7B2%7DM_tV_%7Bit%7D%5E2)
![K_i = \frac{1}{2}(1.1)(4.95)^2+\frac{1}{2}(3.55)(2.2)^2](https://tex.z-dn.net/?f=K_i%20%3D%20%5Cfrac%7B1%7D%7B2%7D%281.1%29%284.95%29%5E2%2B%5Cfrac%7B1%7D%7B2%7D%283.55%29%282.2%29%5E2)
![K_i = 22.06 J](https://tex.z-dn.net/?f=K_i%20%3D%2022.06%20J)
And the final K is:
![K_f = \frac{1}{2}M_cV_{fc}^2+\frac{1}{2}M_tV_{ft}^2](https://tex.z-dn.net/?f=K_f%20%3D%20%5Cfrac%7B1%7D%7B2%7DM_cV_%7Bfc%7D%5E2%2B%5Cfrac%7B1%7D%7B2%7DM_tV_%7Bft%7D%5E2)
![K_f = \frac{1}{2}(1.1)(1.8)^2+\frac{1}{2}(3.55)(3.17)^2](https://tex.z-dn.net/?f=K_f%20%3D%20%5Cfrac%7B1%7D%7B2%7D%281.1%29%281.8%29%5E2%2B%5Cfrac%7B1%7D%7B2%7D%283.55%29%283.17%29%5E2)
![K_f = \frac{1}{2}(1.1)(1.8)^2+\frac{1}{2}(3.55)(3.17)^2](https://tex.z-dn.net/?f=K_f%20%3D%20%5Cfrac%7B1%7D%7B2%7D%281.1%29%281.8%29%5E2%2B%5Cfrac%7B1%7D%7B2%7D%283.55%29%283.17%29%5E2)
![K_f = 19.61 J](https://tex.z-dn.net/?f=K_f%20%3D%2019.61%20J)
Finally, the change in the total kinetic energy is:
ΔK = Kf - Ki = 22.06 - 19.61 = 2.45 J
The best position for the person would be outside, under a clear sky, standing up. He should do it sometime between sunset and sunrise, from a day before until a day after the moment of Full Moon.
Answer:
they're more inclined to be violent so A