# ap physics 1 momentum and impulse free response

Torque, rotational statics, rotational kinematics, angular momentum. Can the student model simple harmonic motion mathematically considering dynamics and energy relationships? Springs, pendulums, etc. Does the student understand the varying relations of the law of gravity in dynamic situations such as orbits of planets and other satellites?

Can the student solve electricity problems? Can the student use a graphical representation of a periodic mechanical wave position versus time to determine the wavelength, period, amplitude and frequency of the wave and describe how a change in the frequency would modify features of the representation? Defend a conclusion based on scientific evidence. Distinguish among tools and procedures best suited to conduct a specified scientific inquiry.

How much momentum did this object start with? The initial momentum of this object is going to be two kilograms times the initial velocity, which was 10 meters per second to the right, which is positive 20 kilogram meters per second. So if the initial momentum of the rocket is positive 20 and there was a change in momentum of , the final momentum just has to be Or in other words, since the change in momentum would have to be the final momentum minus the initial momentum, which was positive 20, we could find the final momentum by adding 20 to both sides, which would give us plus 20, which is What's the difference between an elastic and an inelastic collision?

What we mean by an elastic collision is that the total kinetic energy of that system is conserved during the collision. In other words, if a sphere and a cube collide, for that collision to be elastic, the total kinetic energy of the sphere plus the kinetic energy of the cube before the collision would have to equal the kinetic energy of the sphere plus the kinetic energy of the cube after the collision. If the total kinetic energy before the collision is equal to total kinetic energy after the collision, then that collision is elastic.

It's not enough for the system to just bounce of each other. If two objects bounce, the total kinetic energy might not be conserved. Only when the total kinetic energy is conserved can you say the collision is elastic.

For an inelastic collision, the kinetic energy is not conserved during the collision. In other words, the total initial kinetic energy of the sphere plus cube would not equal the total final kinetic energy of the sphere plus cube. Where does this kinetic energy go? Typically, in an inelastic collision, some of that kinetic energy is transformed into thermal energy during the collision.

While masses could bounce during an inelastic collision, if they stick together, the collision is typically called a perfectly inelastic collision, since in this collision you'll transform the most kinetic energy into thermal energy.

And when two objects stick together, it's a surefire sign that that collision is definitely inelastic. So what's an example problem that involves elastic and inelastic collisions look like? Let's say two blocks of mass 2M and M head toward each other with speeds 4v and 6v, respectively. After they collide, the 2M mass is at rest, and the mass M has a velocity of 2v to the right. And we want to know, was this collision elastic or inelastic? Now you might want to say that, since these objects bounced off of each other, the collision has to be elastic, but that's not true.

If the collision is elastic, then the objects must bounce, but just because the objects bounce does not mean the collision is elastic. In other words, bouncing is a necessary condition for the collision to be elastic, but it isn't sufficient. If you really want to know whether a collision was elastic, you have to determine whether the total kinetic energy was conserved or not.

And we can figure that out for this collision without even calculating anything. Since the speed of the 2M mass decreased, the kinetic energy of the 2M mass went down. And since the speed of the M mass also decreased after the collision, the kinetic energy of the mass M went down, as well. So if the kinetic energy of both masses go down, then the final kinetic energy after the collision has to be less than the initial kinetic energy.

Which means kinetic energy was not conserved, and this collision had to be inelastic. Lab: Simple Machines.

Lab: CoR. Lab: Pine Wood Derby Collisions. Activity: Flying pig. Lab: Circular Motion. FRQ: Design a Space station. Lab: Torque. Lab: Simple Harmonic Motion. PhET: Wave on a string. Lab: Speed of Sound. Inquiry Lab: Electrostatics. Verifying Coulomb's law. Watch video The Conservation of Momentum print version. Wednesday, December 11, Momentum Packet 2. Momentum Packet 2 Key. Thus, diminishing the impact force as to avoid hurting ourselves.

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Example Question 1 : Impulse And Momentum. Possible Answers:. Correct answer:. Explanation : Since the collision is completely elastic, we know that both momentum and kinetic energy are conserved. Report an Error. Explanation : It does not matter whether the collision is elastic or inelastic although it would be best to assume that it's inelastic. Since they come to a standstill, their momentums at the moment of collision are equal and opposite: Rearrange to solve for : Plug in the given values from the question and solve:.

Explanation : Since the collision is completely inelastic, momentum is conserved but energy is not. The equation for conservation of momentum is as follows: There are two inital masses with different velocities and one final mass with a single velocity.

Therefore, we can write: Rearranging for final velocity, we get: At this point, we can denote which direction is positive and which is negative. Example Question 4 : Impulse And Momentum.