Answer:
A. 231.77 J
B. 5330.71 J
C. 46 donuts
Explanation:
A. To lift the barbell once, she will have to extend it the full length of her arm. The work done will then be:
W = F * d
Where the force is the weight of the barbell.
F = m * g
Hence, the work done in lifting the barbell is:
W = m * g * d
W = 43 * 9.8 * 0.55
W = 231.77 J
B. If she does 23 repetitions, the total energy she expend will be equal to the Potential energy when the barbell is lifted multiplied by 23:
E = 23 * m * g * d
E = 23 * 231.77
E = 5330.71 J
C. 1 Joule = 4.184 calories
5330.71 Joules = 5330.71 * 4.184 = 22303.69
If 1 donut contains 490 calories, the number of donuts she will need will be:
N = 22303.69/490 = 45.5 donuts or 46 donuts
Sound must travel through a medium/body. Space is a vacuum so there is no medium/body for sound to travel through, so there is no sound.
Answer & Explanation:
1 N-m = 1 Joule
So 82 kJ of energy put into the system during (i).
45 kJ of heat leaves the system, so 82 kJ - 45 kJ = 37 kJ is remaining.
(ii) requires 100 kJ of energy but only 37 kJ is available, so 100 kJ - 37 kJ = 63 kJ of heat energy must be added to the system.
It’s called conservation of energy. The system (the rider) can’t randomly gain energy without something else giving it energy because energy can’t be created or destroyed, only transferred. The pendulum example is beyond popular and you see physics professors doing it all the time. I think your teacher wants you to say it’ll continue forever, but I don’t think it will. The system will most likely lose energy to its surroundings. And there’s things like air resistance which will, overtime, slow it down. So no, it won’t go on forever
