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| Could the work done on an object result in an increase of kinetic energy? |
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| Could you do no net work and yet get tired? |
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Definition
| Yes, for instance when lowering and lifting the same object many times |
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| A conservative force in physics is |
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Definition
| a force that only depends on the initial and final points |
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| The gravitational potential energy is (m is mass, h is height) |
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Definition
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| Is friction a conservative force? |
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Definition
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| The gravitational force between two masses applies |
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| for any masses in the universe |
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| The drag forces and resistive forces are |
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Definition
| the constant speed at which an object moves in a fluid |
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| Resistive forces on regular objects (rocks, raindrops, etc) in air are dominated by |
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Definition
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| For objects moving in liquids you are normally in regime |
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| The direction of the force respect to the increase of potential energy is |
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| If we knew the potential energy could we get the force? |
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Definition
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Term
| From the energy equation in a spring mass system we can derive |
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Definition
| the equation for simple harmonic motion |
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Term
| An object moves near the bottom of a frictionless spherical bowl. If the object starts from rest and you let it go the motion would be |
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| In an oscillating pendulum is the tension doing any work? |
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| Why did the smaller circular track fail the prediction for small oscillations, while the large air track did not? |
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Definition
| the ball roll in the small track while the mass did not roll in the large one |
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Term
| The velocity to escape the gravitational pull of the Earth and never fall back is |
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Definition
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| If the total energy available to an object that wants to leave the Earth is less than zero we call the possible orbit |
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Definition
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| The period of rotation of the space shuttle orbit around the Earth was |
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Definition
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| A person is riding a bicycle. The power required to maintain certain speed is force times velocity. The force due to air friction is the air drag and it is proportional to the velocity squared. The power needed to double the speed is |
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Definition
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Term
| How many watts per square meter does the Sun provide to the Earth? |
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Definition
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Term
| If a particle changes its momentum |
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Definition
| a force must have acted on it |
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Term
| The change of total momentum of a system of particles is equal to |
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Definition
| the sum of external forces only |
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Term
| If the net force on a system of particles is zero, we say that the net momentum is |
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Definition
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Term
| In collision of particles with no outside forces we say that |
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Definition
| the kinetic energy is not always conserved |
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Term
| The center of mass is at point |
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Definition
| that behaves as if all the mass of the object was concentrated there |
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Term
| Two ball with same mass collide with each other in an elastic collision. One ball was at rest before collision, what happens after collision? |
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Definition
| the ball at rest moves while the incoming ball stops |
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Term
| A collision of particles as seen from the center of mass has momentum zero |
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Definition
| before and after collision |
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Term
| As seen from the center of mass, in an elastic collision, the speeds of particles after collision are: |
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Definition
| the same as before but with opposite signs |
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| The ballistic pendulum is used to measure |
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| The engines in rocket Saturn spit out gas at the speed of |
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Definition
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| Two identical rockets with burn the same amount of fuel and increase their speed by the same amount; one started from rest and one was already moving. Which rocket increases its kinetic energy more? |
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Definition
| the rocket that had an initial speed |
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Term
| n circular motion, the tangential acceleration results in a change of |
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Definition
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Term
| The moment of inertia for a set of masses is the sum of |
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Definition
| each mass times the distance square of this mass to the axis of rotation |
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Term
| Can energy be stored in a rotating object? |
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Definition
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Term
| The Crab pulsar rotational speed is |
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Definition
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Term
| The angular momentum of a point-like object depends on |
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Definition
| the location of the origin of observer |
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Term
| What makes the angular momentum of a point-like object change as seen by the same observer? |
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Definition
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Term
| If an object spins around its center of mass then its the angular momentum is |
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Definition
| the same for all observers located anywhere |
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Term
| If an object is free of external torques and is spinning, what would happen if the object increases, by any means, its moment of inertia? |
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Definition
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Term
| A star collapses after it runs out of nuclear fuel. What could happen to it? |
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Definition
| it could be come a white dwarf, neutron star or a black hole |
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Term
| The angular momentum of a point-like object changes if there is |
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Definition
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Term
| The angular momentum of a meter stick about the center of mass is |
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Definition
| the same for all centers of rotation |
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Term
| A ruler is hit at a point away from its center of mass. After the hit the center of mass will move |
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Definition
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Term
| A hula hoop is made to oscillate about a point at its edge. The period of oscillation does not depend on |
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Definition
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Term
| The general orbit of a planet around the Sun is |
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Definition
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Term
| Kepler found that planets move so that |
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Definition
| they trace equal areas in equal times |
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Term
| If for an orbit of a satellite or planet the total energy is negative we have |
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Definition
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Term
| If a sandwich is in a circular orbit and we want to change it to another orbit by slowing it down in a direction tangent to the circle the period of the sandwich will |
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Definition
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Term
| f an object that emits light approaches you its as seen by you light is |
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Definition
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Term
| What fraction of the stars are binary? |
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Definition
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Term
| Inside the event horizon of a black hole |
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Definition
| an object is trapped forever |
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Term
| When an object is in pure roll the speed of the center of mass is |
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Definition
| equal to the angular speed times radius |
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Term
| Two solid cylinders of the same mass, but one is smaller than the other, roll down an inclined plane, which one gets to the bottom first? |
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Definition
| they arrive at the same time |
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Term
| The angular momentum when changing moves in the direction |
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Definition
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Term
| A bicycle wheel is spinning about its axis. If we support the wheel with a string at the end of one handle, what would happen? |
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Definition
| the wheel will precess (rotate) about the axis of the string |
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Term
| The spin angular momentum has the property of |
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Definition
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Term
| What are the conditions for equilibrium of a rigid body? |
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Definition
| sum of forces and sum of torques both equal zero |
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Term
| A ladder is set on the floor near a wall. The ladder is at a critical angle so that it is ready to slide. A person steps at the bottom of the ladder then the ladder becomes |
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Definition
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Term
| If you have a tube with and a rope wrapped around it so that the ends of the rope support a load each. Due to the friction the rope experiences with the tube we could |
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Definition
| put a very large load on one end of the rope and small load on the other |
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Term
| If you have an object with random shape. How could we find its center of mass? |
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Definition
| Find the point where two vertical equilibrium lines meet |
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Term
| A ropewalker to be very stable could use a long bent bar with extra weight at the ends so that |
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Definition
| the center of mass is below the rope |
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