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Concept Review: Track Those Spots!

Newton's Laws:

Newton's 1st Law

A body at rest tends to remain at rest. A body in motion tends to remain in motion at a constant speed in a constant direction unless acted upon by an outside, unbalanced force.

Newton's 2nd Law

The acceleration of a body is inversely proportional to its mass and directly proportional to the force applied.

Newton's 3rd Law

For every force there is an equal reaction force in the opposite direction.

About the latitude/longitude grid and geometry:

On the latitude/longitude grid, the longitude lines are drawn at 10o increments. (Remember, if they were drawn at 1o increments, there would be 360 circling all the way around the sun!)

Latitude lines are also are drawn at 10o intervals. (Remember, the northern pole of the sun would be at 90o N and the southern pole is at 90o S.)

Displacement, velocity and acceleration:

Converting distance from degrees to radians

A full circle contains 360o or

2 pi radians

Degrees = # of degrees

Radians = # of radians

360o = 2 pi rad

180o = pi rad

Calculating average velocity

Average velocity is the rate of change of distance

Don't forget - velocity is a vector quantity with a direction.

Average angular velocity:

Angular distance / time

w = q/t

Linear average velocity:

linear distance / time

v = d/t

Calculating centripetal acceleration

Centripetal acceleration is the type of acceleration an object has because it is moving in a circle (not a straight line.)

We assume here that average velocity is constant.

Don't forget - the direction of centripetal acceleration is always toward the center of the circular path.

Using translational velocity

ac = v2 / r

Since v = rw, you can substitute rw for v in this equation to obtain centripetal acceleration

using angular velocity:

ac = w2 r

Note: in both cases r = path radius

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NASA Logo Image Author: Mitzi Adams, mitzi.adams @ nasa.gov
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Last Updated: September 12, 2017