51 Cards in this Set
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Work
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Scalar quantity, =Fcos()d, force through a distance
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What is on Joule equal to?
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1 N x 1m
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If an object is moving with constant velocity, what is the net work?
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zero, constant force means no acceleration which means no net force
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Equation for force by a spring
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F=-k(x-x0)
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Equation for work from a spring
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W=(.5)k(x2-x02)
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What is work done on an object equal to?
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W=(.5)m(vf2-vi2)
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What is kinetic energy defined as?
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(.5)mv2
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How is work done on an object related to change in kinetic energy?
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they are equal
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What is potential energy?
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energy associated with configuration of a system of objects
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What is the equation for gravitational potential energy (U)?
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Uf-Ui=mgh=W
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Law of conservation of total energy
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the total energy of an isolated system is always conserved
Ef=Ei
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What is energy equivalent to in terms of kinetic and potential energy?
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E=K+U
therefore
(K+U)f=(K+U)i
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What direction is friction always relative to the motion?
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the opposite direction of the motion
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Friction is an example of a nonconservative force.. explain
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it changes the mechanical energy of the system, it makes the work done dependent on the path
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Work done by nonconservative forces reflects what?
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the mechanical energy lost, the total energy of the system is the same, but is in the form of neither mechanical nor potential energy
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What is Power equal to?
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P=W/t (Watts)
P=Fd/t=Fv
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What is the equation for efficiency?
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e=Wout/Ein x100%
e=(Pout/Pin) x 100%
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Can we treat systems of particles as one big particle when considering center of mass?
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yes
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The point at which the total mass of a system is concentrated is known as...
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center of mass
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how does the center of mass move?
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as if all mass of system were concentrated at that point, consider a thrown hammer
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how do we find the location of the center of mass in X Y coordinates?
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For X and Y... XCM=(sum of mixi)/Msystem
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Does the center of gravity of a nonsymetric object lie within the object always?
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no!
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What is angular displacement?is change in theta a distance?
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the angle through which the object rotates, it is not a distance. theta= theta-theta0
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what is theta equal to in terms of radians?
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Arc length (s)/Radius (r)
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what is the conversation between degrees and radians
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2pie rad= 3600
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what is angular speed?
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the rate at which angular displacement is changing( omega=(change in theta)/time)....units are rad x s-1
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what does tangential speed tell us? what is it equal to?
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how fast something is moving along the circle... vt=r(omega)
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what is frequency? how does it relate to angular speed?
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number of cycles per second... w=2piexf...units are s-1 or Hz
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What is period and how does it relate to angular speed?
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time it takes for a circular motion to complete a cycle.. w=(2pi)/T
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Angular acceleration
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change in angular speed
alpha=(change in theta)/time
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In uniform circular motion, which is constant, tangential speed or tangential velocity?
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tangential speed
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which direction is centripetal acceleration always?
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towards the center of the circle
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which direction is tangential acceleration always?
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it is always changing as the object moves circularly
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In uniform circular motion, must there be a net force to produce a centripetal acceleration?
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yes, Fc=m(v2/r)
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what provides the force needed for centripetal acceleration on an unbanked curve?
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static friction
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what are the two types of motion that rigid bodies have?
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translational and rotational
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Translational motion
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all particles have the same linear velocity
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rotational motion
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all particles have the same angular speed
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rolling is a combination of..
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translational and rotational motion
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if no slipping occurs, what is the relationship between arc distance and distance traveled?
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they are equal
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What are the first and second conditions for equilibrium
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first: the net force on the object must be zero
second: the net torque on the object must be zero.
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Torque (w/ equation)
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the ability of a force to cause rotation of an object. T=rFperpendicular
or T=rFsin(theta)...or cosine, whichever gives you the perpendicular component of the force to the r
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Torque is a vector and there for has direction... which is positive? which is negative?
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positive= counterclockwise
negative= clockwise
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when determining theta, what is the angle we want to use in torque?
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tip to tail of tip of r to tail of foce
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If the center of gravity is outside the base of support...
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the gravitational torque will cause the object to tip over
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What is newtons second law in terms of rotation?
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Torquenet=Angular acceleration x moment of inertia
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Objects with large moments of inertia are
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more difficult to rotate
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Moment of Inertia
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∑mr^2
an objects resistance to a change in rotation
- choking up on baseball bat
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What is the equation for work in a circular motion?
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W=t(theta)
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rotational kinetic energy
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KE = ½Iω²
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Rolling Object Kinetic Energy
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KE = ½mvcm² + ½Iω²
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PHY 103: Exam 1