course Phy 201 |??????????assignment #027?>???????y????Physics I
......!!!!!!!!...................................
22:00:59 Query intro probs set 7, 1-7 Knowing the 9.8 m/s^2 gravitational field strength of the Earth's field at the surface of the Earth, and knowing the radius of the Earth, how do we find the gravitational field strength at a given distance 'above' the surface of the Earth?
......!!!!!!!!...................................
RESPONSE --> we first find the inverse square of the ratio between the two radii. This is then multiplied by 9.8m/s^2 to find the field strength.
.................................................
......!!!!!!!!...................................
22:01:02 ** You have an inverse square force. Square the ratio of Earth radius to orbital radius and multiply by 9.8 m/s^2: Field strength=(Re/r)^2*9.8m/s^2 **
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
......!!!!!!!!...................................
22:01:17 If we double our distance from the center of the Earth, what happens to the gravitational field strength we experience?
......!!!!!!!!...................................
RESPONSE --> we lessen the force by 1/2^2=1/4
.................................................
......!!!!!!!!...................................
22:01:19 ** We have an inverse square force so if r2 = 2 * r1 the ratio of the gravitational field will be g2 / g1 = (1 / r2^2) / (1 / r1^2) = r1^2 / r2^2 = (r1 / r2)^2 = (r1 / (2 * r1))^2 = r1^2 / 4 r1^2 = 1/4. In a nutshell double the radius gives us 1 / 2^2 = 1/4 the gravitational field. **
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
......!!!!!!!!...................................
22:03:45 How do we approximate the energy required to move a given mass from the surface of the Earth to a given height 'above' the Earth, where the field strength at the given height differ significantly from that at the surface?
......!!!!!!!!...................................
RESPONSE --> first the force must be established at the base and at the top, then these averaged to find the average force necessary to raise the object the height. this average force is then multiplied by the distance to establish the work necessary to raise the object.
.................................................
......!!!!!!!!...................................
22:03:48 STUDENT SOLUTION AND INSTRUCTOR RESPONSE: mass*[(Re + distance)/Re]^2=force Force*distance=KE INSTRUCTOR RESPONSE: The first approximation would be to average the force at the surface and the force at the maximum altitude, then multiply by the distance. The result would give you the work necessary to 'raise' the object against a conservative force, which would be equal to the change in PE. ADDENDUM FOR UNIVERSITY PHYSICS STUDENTS ONLY:The exact work is obtained by integrating the force with respect to position. You can integrate either G M m / r^2 or g * (RE / r)^2 from r = RE to rMax. **
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
"