Final May Flashcards
We claim that momentum is conserved yet all moving objects eventually slow down and’s top explain
Momentum is scorn served Ina.closed system therefore when an object slows down and stops it is becuase the momentum is being transferred to teh earth but because the velocity and onetime is so small it is nonexistant to us
Compare and contrast elastic and in elastic collisions
In both elastic adn in elastic collisions memo gum is conserved however in elastic collisions kinetic energy is also conserved while in in elastic collesisions kinetic energy is not conserved
Exaplin in detail why it is more difficult to do sit ups with your hands behind your head than when your arms are stretched out in front of you**
Behind the head becuase the arms are getting farther away from the axis of rotation and so there is a greater radius and greater rotational inertia
Suppose you are sitting on a rotating stool whihc is rotting, holding 2-kg mass in each outstretched hand. If you suddenly bring your arms closer to your body will your angular velocity change, how? Will your angular momentum change? How?**
Angular velocity will increase because the radius is decreasing so less rotational inertia, angular momentum no bc comserved
A sphere and a cylinder have the same radius and same mass, they start from rest at the top of a incline, whihc will reach the bottom first, which has the greater speed at the bottom, which has the greater total kinetic energy t the bottom, whihc has the greater rotational energy, explain in detail **
The sphere becuase less rotational inertia , the speed and total kinetic energy is the same becuase the energy is conserved, the greater rotational energy is the cylinder while the sphere has greater translational energy
Two inclines have the same height but make different angles with the horizontal, if the ball rolls without slipping on which incline will teh speed of the ball at the bottom be greater, on which will teh time down the incline be greter**
Speed is the same bc energy is conserved the shorter one will take longer becuase it’s a greater distacne for it to reach the same speed and less component of gravity so it takes longer to accelerate compared to the greater taller one
Can a centripetal force every do work on a object
No a centripetal force can never do work on an object because the path of hte velocity is tangential (erpendicular) not parallel
can a normal force ever do work on an object
Yes the normal force can do work on an object, like lifting the object up or when a passenger jumps on the elevator, teh elevator works on teh passenger as a normal force
Cars used to be built as rigid as possible to withstand collisions. Today though care are designed to have crumple zones that collapse upon impact, what is the advantage of this new design
The longer the collision the less froce and impact, therefore with teh crumple zones the collisions lasts longer making teh impact smaller specially on teh driver and passengers
The form of coulumbs law is very similar to that of Newton’s law of univweersal gravitation what are the similarities and differences between these two laws
Both have a constant both have product of fundamental property- product of masses adn product of charges, inverse square, Coulomb’s has large constant Newton has small constant Coulomb’s is both attractive or repulsive Newton is attractive only– shows that mass and charge there’s only one mass and two kinds of charges no direction of mass but yes fro charge
Contrast net charge on a conductor to the free charges in a conductor
net charge is excess unbalance between positive or negative charge and free charge is always there for metals valence electrons that are free to move around
Why is it that electric field lines can be closely spaced but never cross
The electric field lines can be closely spaced but never cross because they are vector quenstites therfoer because they are vector quantities they have magnitude and direction so if the lines cross that means that one charges have the same magnitude and two direction at the same time which can’t happen so teh field lines don’t intersect
Explain why test charges we use when measuring electric fields must be small a dn why they are positive
They a re small so that they don’t interfere with the electric field lines and positive by convention becuase they needed consistency so they chose the positive
