# Physics 101 Test 3

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valleystudent84's
version from
2015-10-19 14:45

## Section

Question | Answer |
---|---|

Gravity increases with the _ and _ of two objects | Size - Proximity |

Inverse Square Relationship - Define | The gravitational force is inversely proportional to the square root of the distance [between two objects] |

If the distance between two objects is doubled than the gravitational force is _ as big | 1/4 |

Law of Universal Gravitation - Define - equation | ALL objects have a gravitational pull between them - F=G[(m1xm2)/(r^2)] |

G in Universal Gravitation equation = | 6.67x10^-11 (Newtons x meters^2)/(Kilograms^2) |

The gravity between objects on earth is hardly felt because of the LARGE force of gravity exerted by the _ on each object | Earth |

Geosynchronous - Define | The distance from earth where a satellite would stay above a specific part of the earth and rotate at the SAME speed as the earth. Crazy!! |

T or F. The moon orbits the earth | False. They actually both orbit the center of mass for the "earth-moon system." The two objects have an equal and opposite pull on each other, but because earth has much more mass the center of this system is much closer to the earths center (located under the earths surface.) |

Explain the Tide with the moon | As the earth and moon accelerate towards each other, the side of the earth that is CLOSER to the moon is "falling faster" (because it is closer to the moon and is therefor more affected by the gravity of the the moon; the ocean is pulled by the gravity of the moon |

Does the sun affect the tide on earth? does anything else also affect it? | Yes - ALL orbiting bodies have an effect on ALL other orbiting bodies |

Does the land experience tidal movement? | Yes!!! |

Field Concept - Define - Steps | Determine the force exerted by an object and then calculate the force exerted on a second object - Step 1(an objects Mass exerts a gravitational field at every point in space) STEP2 (The second object interacts with the field created by the first by virtue of its mass) |

Field - Define | A region of space that has a number of vectors assigned to every point |

Linear momentum - define - equation - units | The product of an objects mass and its velocity - p=mv - (Kg)(m/s) |

Momentum - define | How hard it is to stop an object |

T or F, a parked truck has momentum | False, an object needs velocity to have momentum |

Impulse - define | Applying a net force on an object for a certain amt of time; a change in an objects momentum |

T or F, impulse is NOT a vector Qty | False, impulse is the change in velocity x the mass |

Why do you want to land on a softer surface after a fall? | When a surface "gives" there is a longer collision time ; the AVE F(net) is smaller |

Why do cars have air bags? | the airbag allows for a longer collision time during an impact |

What are the two ways to change an objects momentum | mass - velocity |

Change in Ug equation | ΔUg=Ug(f)-Ug(i) |

PGE is alao called | Ug |

Change in Momentum Equation | Δp=p(f)-p(i) |

Magnitude of Δp is equal to | IΔpI |

T or F, a skateboarder needs a 0 F(net) between themselves and the board to balance on a skateboard | True, if either the person or the board have a larger F(net) the person will fall. |

Is a person on a skateboard a closed system? does the conservation of momentum change if you DO NOT fall? | Yes - No |

If a QTY in a closed system does not change after going through a series of changes we say that there is a _ of that QTY | Conservation |

Conservation of Linear momentum - define | The sum total of ALL linear momentum forces acting in a CLOSED system. |

Use conservation of momentum to explain how a propeller driven plane flies through the air | the propellers have a momentum which causes the air to flow BACKWARDS. This momentum is countered by the FORWARD momentum of the plane. |

how does a balloon fly through a vacuum - does this process need air? | the escaping gasses have a momentum that propels them BACKWARD which propel the balloon FORWARD. - NO AIR IS NEEDED IN THE SPACE |

If an equation does not EXPLICITLY have time _ is conserved | Energy |

If an equation does not EXPLICITLY depend on a translation in space, _ is conserved | Linear Momentum |

If an equation does not EXPLICITLY depend on rotations of space, _ is conserved | Angular Momentum |

Impulse is in the _ direction as the _. this is also the same direction as the _ | same - Force - momentum |

A _ is required to change the momentum of an object | Force |

Change of an objects momentum equation | ΣF = Δp/Δt |

Impulse-momentum theorem - equation | The change in the momentum of an object is equal to impulse of the F(net) acting on the particle - Δp=I (impulse is being applied by a Force) |

Elastic Collision - Define | Total kinetic energy before the collision is = to the kinetic energy AFTER the collision; total kinetic energy is conserved |

Inelastic collisions - define | The kinetic energy is NOT conserved; energy before does NOT equal after collision. Some energy is lost as THERMAL energy |

Kinetic Energy equation | KE=(1/2)(m)(v)^2 |

Most common type of energy is_ energy | Kinetic |

The KE of an object increases with the _^2 | Speed |

If an object DOUBLES it speed, the KE is _ times as large | 4 times as big |

The KE of an object is _ proportional to its mass | Directly |

Unit for ALL energy is_. SI unit is _ | (Kg)(m^2/s^2) - joule (J) |

T or F. KE is a vector Qty | False, the KE is NOT dependent on the direction of motion |

Elastic Collision - Define | The initial KE is = to the Final KE |

Inelastic Collision - Define | KE before collision is NOT = to KE after collision |

Perfect inelastic collision - Define | Extreme inelastic collision in which the colliding objects stick together after the collision. |

Outcome of collisions are determined by the _ of _ AND the extent to which KE is _ | Conservation of momentum - Conserved |

If you drop a rubber ball on a hard surface and it returns to its ORIGINAL height, the collision is _ | elastic, because the KE is the same before and after the collision. (would never happen) |

Conservation of energy - define | Energy is never created or destroyed, it just changes states (heat, potential, KE, etc) |

A _ is needed to for a change in KE | F(net) |

Work equation - units | F=(force)(distance) - J (Also N*m, which is the same thing) |

In order for work to be done there MUST be _ | Motion |

Work is ALSO defined by _ (involves KE) | ΔKE |

F(net) and velocity in SAME direction = what kind of work? | Positive work |

F(net) and velocity in OPPOSITE direction = _ kind of work | Negative work |

T or F, momentum is a force | False, momentum is a Qty of motion |

A car slowing down is an example of _ work - explain | Negative work - the brakes apply a force that is OPPOSITE to the rotation of the wheels and is therefor negative, but because this force is applied WITHIN the same object its force is small. The roads friction force with the wheels is what does most of the slowing |

A car traveling at 25 mph has only _ the KE as one traveling at 50 mph. | 1/4 |

For work to happen the forces have to be along the _ of _ | Direction of motion |

Forces that are perpendicular to the motion of and object do _ work | No |

In a constant circular motion there is _ work being done - explain | none because the forces are perpendicular to the motion |

T or F. As a ball goes up vertically it INCREASES in KE | False, the ball would be gaining PE |

Gravitational Potential Energy (GPE) - Define - also shown as | The work that WOULD be done by gravity if an object fell from a particular point in space to the location assigned a value of 0 - Ug |

GPE equation - units | GPE=(mass)(accel of gravity)(height) - J |

T or F. GPE increases as KE decreases | True |

The GPE of an object at height X is = to ? | the acceleration of gravity of the same object dropped the SAME distance ABOVE height X |

T or F. moving an object horizontally changes the GPE | False |

Mechanical Energy - define - equation | The sum of KE and ANY types of potential energy. - ME=KE+(all types of) PE |

T or F. When friction force can be ignored and only GPE is doing work, the ME of a system does NOT change - example | True - free fall |

In a swinging pendulum, the MAX GPE is at _ and the MAX KE is at _ | top of swing - middle of swing |

A spring is an example of what kind of PE? | Elastic PE |

Chemical energy is PE associated with what phenomena | Electro-magnetism |

When friction forces interact with KE, what is created? | Thermal energy |

Power - define - equation - units | The change of energy from one type to another with respect to time - P = ΔE/Δt - W or (J/s) |

Power measurement for ME | Horse power |

1 Horse power = _ watts | 746 |

KE is transformed into other forms of E during _ collisions | Inelastic |

KE is = to what amount of W done on the object | Same amount |

T or F. KE can change into friction E - explain | False - if friction is involved, the energy is transferred into Thermal energy. There is no such thing as Friction energy. |

Work-energy Theorem - equation | The work done on an object is equal to the change in its KE - ΔK=K(f)-K(i) |

Elastic Potential energy also called _ | U(s) |

1 watt = _ J/s | 1 J/s |

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