The momentum of a photon is given by the following relationship:
where
h is the Planck constant
is the photon wavelength
For the photon in our problem,
, so its momentum is
The electron must have the same momentum of this photon, and its momentum is given by (in the non-relativistic approximation)
where
m is the electron mass
v is its speed
Re-arranging this formula, we can calculate the electron speed:
And this velocity is quite small compared to the speed of light (
), so the non-relativistic approximation that we used for the electron's momentum is valid.
F n = ma / unbalanced force - In the direction of the force.
<span>Yes, it's possible to hoist the child up.
Let's first determine the maximum amount of pull that the woman can exert. That will be the simple product of her weight and the coefficient of static friction with her shoes and the ground. So
0.8 * 190 = 152.
So far, so good, since 152 is greater than the boy's 80 lbs. But the cable rubs at the cliff edge and that means that the lady has to pull harder. Let's see how much harder.
There will be 80 lbs of tension on the cable, pressing against the cliff edge. So let's multiply by the coefficient of friction to get how much that is
0.2 * 80 = 16
So friction will take 16 lbs of effort to overcome. So the lady needs to pull with 80 + 16 = 96 lbs of force to move the boy. And since we've determined earlier that she can pull with up to 152 lbs of force, she can easily hoist the child up.</span>
Answer:
Rest
Explanation:
Rest is a change in the position of a body with respect to time relative to a reference point. The stationary state of an object or body relative to a reference position or another object is called Rest.
Taking Newton's First Law of motion into consideration, an object will remain in its state of rest or uniform motion until acted upon by an external force. This implies an object at rest is an object with zero (without) velocity and acceleration.
Sinkholes and caves are 2 reasons. hope that helped
