Term
| What is the most important noncontact force? |
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Definition
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Term
| What is Newton's Law of Gravitation state and what is the formula? |
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Definition
It describes the concept of gravity. Any two particles attract one another with a force directly proportional to the product of their masses and inversely proportinal to the square of their distances between center of mass
F = (G x m1 x m2) / r^2 |
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Term
| What is weight? And what is the equation? And units? |
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Definition
It is a vector quantity and it is the attractive force of the earth on an object
W = mg (newtons), where g = 9.81m/s^2 |
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Term
| What are the units of mass? |
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Definition
| it is a scalar quantity and it is kg |
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Term
| What is the effect produced by gravity? |
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Definition
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Term
| Is the acceleration due to gravity the same everywhere on the earth's surface? |
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Definition
| No, because the points on the earth are not equidistant from its center! Not perfect spherical |
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Term
| Through what point does the resultant force act on a body? |
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Definition
Through the center of gravity (CG).
Does not always have to be within the physical limits of the body |
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Term
| What are the forces that influence a projectile's flight? |
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Definition
| Gravity (vertical only) and Air resistance (always opposes motion, we will use negligible air resistance) |
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Term
| What are the (3) factors we control to manipulate flight trajectory? |
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Definition
Speed of release, and
height of release, and
angle of release, |
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Term
| What is the point in time at which an object is considered a projectile? And what is the flight path of a projectile called? |
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Definition
| The instant of release. It's called a trajectory. This type of motion has no external forces acting on it except for gravity and air |
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Term
| Without air resistnace, a projectile's flight path is called what? And what is the highest point called? |
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Definition
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Term
what happens to d(horizontal) in each of these cases:
speed increase.. dh ..?
heigh increase.. dh ..? |
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Definition
speed increase.. dh ..increases
height increase.. dh ..increases, because vh is the same BUT t(tot) increases because the object has farther to fall |
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Term
| How do we know if motion is angular? |
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Definition
| If 2 pts on the same body move different distances in a given time |
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Term
| if h=0, what is the optimal angle of release for a projectile? |
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Definition
| 45 degrees. 30 degrees and 60 degrees will have a shorter horizontal distance |
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Term
| If speed is held constant, what happens to the optimal angle as you increase the height? |
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Definition
| the optimal angle decreases AWAY from 45 degrees |
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Term
| If height is held constant, increasing the speed of release results in what for the optimum angle? |
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Definition
| getting closer to 45 degrees |
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Term
| to which factor is d(horizontal) most sensitive to? |
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Definition
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Term
| What is a very important feature of human motion? |
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Definition
| Segment rotations combine to produce linear motion of the whole body |
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Term
| Key concept: motion of any point on a rotating body can be described in linear terms. What info is required? |
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Definition
1. axis of rotation
2. location of point of interest relative to axis |
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Term
| What are the units for angular velocity? What are the units if you are using angular velocity in an equation? |
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Definition
| degrees/s but if you are using it in an equation it must be in radians/second! |
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Term
| what is the formula for linear and angular displacement? and what units? |
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Definition
d=(theta)(r)
where d is the linear dist the point of interest has traveled
theta is the angular dist
and r is the linear distance that the point of interest is located from the axis
theta MUST be expressed in radians!!!!!!!!! |
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Term
| what is the formula for linear and angular velocity? |
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Definition
V(tangential)=w x r
w - angular velocity in rad/s!!!
r - radius of rotation of point of interest |
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Term
| how do you convert from degrees to radians? |
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Definition
divide the degrees by 57.3 to get radians
multiply the radians by 57.3 to get degrees |
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Term
| what are you doing if you are maximizing v(tangential)? aand how do you do it? |
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Definition
you are maximizing the linear velocity of a point located distally on a rotating body
maximize vt by...
increase w
increase r
increase both |
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Term
| why is it difficult for an athlete to maintain w if r is increased, vice versa? |
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Definition
moment of inertia
think of a sledge hammer |
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Term
| What happens during linear and angular acceleration, what is the object forced to do? |
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Definition
| Follow a curved path due to inertia. The continuous change in direction represents change in direction of velocity i.e. acceleration! |
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Term
| what is centripetal acceleration? |
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Definition
| the linear acceleration that describes the change in the DIRECTION of v(tangential) of an object foloowing a curved path (aka radial acceleration) |
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Term
| what is tangential acceleration? |
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Definition
| a(t) - the linear acceleratoin that describes the rate of change in MAGNITUDE of tangential velocity |
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Term
| give an example of centripetal acceleration and its effects |
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Definition
| as a hammer thrower spins just before release, the hammer follows a curved path. at release, there is no more centripetal force and the hammer takes off along a tangent line |
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Term
| explain the physics of a sprinter running a curve |
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Definition
| they are continual undergoing a change in direction, i.e. there is an a(centripetal). |
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Term
| for all rotational and curvilinear motions, resultant acceleration = |
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Definition
| the vector sum of the centripetal and tangential accelerations |
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Term
| what is the formula for centripetal acceleration? and what happens if you change some of the variables? |
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Definition
a(c)=[v(t)^2]*r = (w^2)*r
if you increase v(t), higher force is needed to maintain curved path (produce ac)
if you decrease r (radius), results in higher ac, also need greater force to maintain curved path |
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Term
| what is the advantage of banked turns? |
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Definition
| banking faciltates development of centripetal force, so less dependent on friction as a source of centripetal force |
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