sierravick123owr441
21.01.2021 •
Physics
Which of the following statements is true?
Efficiency is calculated by multiplying work input and work output.
Only a few machines are 100 percent efficient.
Some machines are frictionless.
The ratio of work output to work input is always less than one.
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Ответ:
The ratio of work output to work input is always less than one.
Ответ:
It only depends on the vertical component
Explanation:
Hello!
The horizontal component will tell you how much you travel in that direction.
You could have a large horizontal velocity, but if the vertical velocity is zero, you will never be out of the ground. Similarly, you could have a zero horizontal velocity, but if you have a non-zero vertical velocity you will be some time off the ground. This time can be calculated by two means, one is using the equation of motion (position as a function of time) and the other using the velocity as a fucntion of time.
For the former you must find the time when the position is zero.
Lets consider the origin of teh coordinate system at your feet
y(t) = vt - (1/2)gt^2
We are looking for a time t' for which y(t')=0
0 = vt' - (1/2)gt'^2
vt' = (1/2)gt'^2
The trivial solution is when t'=0 which is the initial position, however we are looking for t'≠0, therefore we can divide teh last equation by t'
v = (1/2)gt'
Solving for t'
t' = (2v/g)