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ch 8 physics
| Question | Answer |
|---|---|
| Circular motion | When an object turns about an internal axis, rotation |
| Two kinds of circular motion | tangential (linear speed) or rotational (circular speed) |
| Tangential Speed | distance traveled by a point on the rotating object divided by the time taken to travel that distance, symbol v (italized) -points closer to the circumfrence have a higher speed than closer to the circle. |
| Rotational speed | number of rotations or revolutions per unit of time. - ex all parts of a rigid merry-go-round or turntable about the axis of rotation in the same amount of time. |
| Tangetial speed equation | v = r w which is Radial distance x rotational speed |
| A ladybug sits halfway between the rotational axis and the outer edge of the turntable. When the rotational speed of 20 RPM and the bug has a tangetial speed of 2 cm/s what will be the rotational and tangetial speeds of her friend who sits at outer edge | 20 RPM, 4 cm/s |
| Rotational Inertia (capitol I) | - An object rotating about an axis tends to remain rotating about the same axis at the same rotational speed unless interfered w/ by some external influence. -The property of an object to resist changes in its rotational state of motion is (symbol I) |
| Rotational Inertia depends on | - mass of object, larger mass larger inertia - distribution of mass around axis of rotation (greater distance between mass concentration and axis, greater rotational inertia) - what rotating around |
| A hoop and disk are released from the top of an incline at the same time, which one will reach first. | the disk because it has smaller inertia because the mass is closer to the axis then the hoop. |
| Torque | tendency of force to cause rotation |
| What does torque depend on | - magnitude of force - direction in which it acts - the point at which it is applied on the object |
| Torque equation | = Lever arm x force - lever arm depends on: where the force is applied and the direction in which it acts |
| Center of Mass | Average position of all the mass that makes up the object |
| Center of Gravity (CG) | average position of weight distribution |
| Center of Mass and Center of gravity usually refer to | the same point of an object. |
| Centripetal Force | Any force directed toward a fixed center "center-seeking" |
| Centripetal Force depends on | -Mass of an object -Tangential speed of the object -radius of the circle |
| Centripetal Force equation | (mass x tangential speed^2) / radius or Fc = mac = m (v^2)/(r) |
| if you double the speed at which you round a bend in the curve, by what factor must the centripetal force change to prevent you from skidding? | four times because of ^2 |
| Suppose you take a sharper turn than before andhalve the radius by what factor will the centripetal force need to change to prevent skidding | double because radius is now halved. |
| Centrifugal Force | occupant inside a rotating system seems to experience an outward force. -"center-fleeing" |
| Angular Momentum | "inertia of rotation" = rotational inertia x angular velocity which is linear momentum = mass x velocity. |
| Suppose you are swirling a can around and suddenly decide to pull the rope in halfway; by what factor would the speed of the can change? | A. Double Because angular momentum is proportional to radius so i radius is halved the speed doubles. |
| Law of Conservation of Angular Momentum | If no external net torque acts on a rotating system, the angular momentum of that system remains constant. |
| Suppose by pulling the weights inward, the rotational inertia of the man reduces to half its value. By what factor would his angular velocity change? | A. Double angular momentum is proportional to rotational inertia so if rotational inertia is halve but angular momentum is constant the velocity would double |
Created by:
edw13
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