A rock at the edge of a cliff has potential energy because it isn't in motion, but is located in a place that motion could occur in the near future.
Answer:
(D) the spot could have been caused by an object that emitted a flash that lasted for only a fraction of the time that the camera shutter was open
Explanation:
(A) the spot was not the brightest object in the photograph: The effect described and the brightness of the objects have no relation. Stars of very different brightness will be shown.
(B) the photograph contains many streaks that astronomers can identify as caused by noncelestial objects: Yes, but that doesn't explain the effect described. A plane could leave a streak.
(C) stars in the night sky do not appear to shift position relative to each other: True, at least for relative short times, but that has nothing to do with the effect described, which happens in a very short period of time.
(E) if the camera shutter had not been open for an extended period, it would have recorded substantially fewer celestial objects: True, but quantity of objects does not relate with the particular case described.
(D) the spot could have been caused by an object that emitted a flash that lasted for only a fraction of the time that the camera shutter was open: True, this can happen, for example, with Iridium satellites, they emit a flash (reflect solar light) that lasts a very short time as seen from one point on the surface (the place where the camera is), and something like this could have been captured by the camera shutter, appearing like a point compared to the streaks left by the stars.
Answer: 6611.715 joules
Explanation:
Q = MxCxdeltaT = 6959.7 which is 100%
95% = 6611.715
Answer: Torque= tangential force × radius of the pulley
Explanation:
Pulley is a simple machine which helps us to lift loads by applying the force in a convenient direction. It consists of a grooved wheel which is free to rotate about an axle passing through the center of the pulley.
For a pulley, the torque 
tangential force × radius of the pulley
Pulleys can be used in combination also to achieve a desired output.
Answer:
m = 170 g
Explanation:
Meter stick is suspended at 40 cm mark
So here the torque due to additional mass and torque due to weight of the spring must be counter balanced
given that
1) 220 g is suspended at x = 5 cm
2) 120 g is suspended at x = 90 cm
3) mass of the scale is acting at its mid point i.e. x = 50 cm
now with respect to the suspension point the torque must be balanced
so we have
by solving above equation we have
m = 170 g
