# HPhys7

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 Author: doctorwhogirl998 ID: 189624 Filename: HPhys7 Updated: 2012-12-15 13:03:28 Tags: Physics Folders: Description: Physics: Circular Motion and Gravitation Show Answers:

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1. Circular motion:
• motion with constant radius of curvature caused by acceleration being  to velocity.
• A body moving in uniform circular motion has a constant speed and is accelerated toward the center of the circle.
2. Tangential speed
is the speed of an object in circular motion. (the v in the following formula)
3. Centripetal acceleration:
acceleration toward center of circular motion;  ac = v2/r
4. Period:
time needed to repeat one complete cycle of motion (T).
5. Centripetal force:
force that causes centripetal acceleration
• is also toward the center.
• is necessary for circular motion.
6. Newton’s Law of Universal Gravitation:
• Gravitational force is the mutual force of attraction between particles of matter.
• Orbiting objects are in free fall.
7. F between 2 bodies depends on
• 1. product of their masses
• 2. divided by the square of the distance between them
• F α
8. Newton’s law of gravitation accounts for?
• ocean tides.
• Gravity is a field force.
• Gravitation field strength equals free-fall acceleration.
• Weight changes with location.
9. Kepler’s laws of planetary motion:
• 1. planets move in elliptical orbits
• 2. planets sweep out equal areas in equal times
• Both the period and speed of an object that is in a circular orbit around another object depend on two quantities: the mass of the central object and the distance between the centers of the objects.
10. Torque and Simple Machines
• If you want to make an object move, apply a force.
• If you want to make an object rotate, apply a torque.
11. Torque
• is a quantity that measures the ability of a force to rotate an object around some axis.
• Torque = product of force and the lever arm.
•  Γ = Fdsinθ
12. Lever arm:
distance from axis of rotation to a line along which the force acts.
13. A machine eases the load either by changing the magnitude or the direction of the force exerted to do work but does not change the amount of work done.  A machine provides a mechanical advantage.
14. 6 simple machines:
lever, pulley, wheel & axle (gears = wheel & axle), inclined plane, screw, wedge.
15. Compound machine is two or more simple machines linked so that Fr of one machine becomes the Fe of the second; AMA of a compound machine is the product of the AMA’s of the simple machines it is made up of.

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