Why do scientists look for asteroids that might strike our planet?
2 answers:
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Answer:
Wp = 1,272 J
Wf = -940.8 J
Wn = 0
Wg = 0
Explanation:
- Applying the definition of work, as the product of the component of the force applied, along the direction of the displacement, times the displacement, we find that due to the normal force is always perpendicular to the surface, it does no work, as it has not a component in the direction of the displacement, so Wn = 0.
- As the weight goes directly downward, it has no component in the direction of the displacement either, so Wg = 0.
- We can get the work done by the force applied P, simply as follows:
- Finally, we have the work done by the force of friction that always opposes to the displacement, so it has negative sign.
- The frictional force , can be written as follows:
where μk = coefficient of kinetic friction = 0.24
Fn = Normal Force
- In this case, since the surface is level and horizontal, and there is no acceleration of the box in the vertical direction, this means that the normal force (in magnitude) must be equal to the weight:
- Fn = m*g = 50 kg * 9.8 m/s2 = 490 N
- Replacing these values in (2), we get:
- Applying the definition of work, we can get the work done by the frictional force, as follows:
Hey! I empathize with you, as I just started the energy unit in physics as well!
Alright, lets list what we know, and which equation(s) we need.
PE = Gravitational Potential Energy
m = mass
g = gravity (9.8 m/s^2)
h = height
Guess what?
We need to find the height!
Lets make this more organized:
Known:
m = 40 kg
PE = 14000
g = 9.8 m/s^2
Unknown:
h = ?
================================
Now, if we take a look at the equation PEg = mgh, you will see that we have everything besides the height! So lets solve for the height by substituting in for the variables we know:
14000 J = 40 kg * (9.8 m/s^2) * h
40 * 9.8 = 392
14000 J = 392 * h
14000/392 = h
35.71 m = h
There we go! If you simply list what you know and don't know, you will find the equation you need to solve the problem.
Have a great day and good luck!