A 20 gram bullet, traveling horizontally with a velocity of magnitude 350 m/s, is fired into a wooden block with a mass of 0.75, initially at rest on a level surface. The bullet passes through the block and emerges with its speed reduced to 150 m/s. What is the kinetic energy of the block (in J) at the instant after the bullet passes through it

The kinetic energy is 10.65 joules.

Explanation:

This case can be considered as a collision if we neglect the frictional forces the ball experiences traveling through the wooden block because are lower than the impact forces, then we can use conservation of linear momentum to model this situation considering the system block-bullet.

Linear momentum states total initial momentum (pi) is equal to the final momentum (pf), this is:

Total momentum is the sum of individual momentums, in our case the momentum of the ball (pb) plus the momentum of the wooden block (pw), then:

Linear momentum of an object is defined as mass times velocity, then:

With vb the velocities of the bullet, mb the mass of the bullet, vw the velocities of the wooden block and mw the mass of the wooden block. Note that the wooden block is initially at rest, that means the initial velocity of the wooden block is zero, then:

Solving the equation for the final velocity of the block:

(Important: i. The sign of the velocities is important, so we chose positive direction as the direction the bullet moves initially, positive velocities means they are in this same direction.

ii. I assume 0.75 kg for the mass of the wooden block because you didn't provide its unities)

Now with the velocity of the bullet after the collision we can find the kinetic energy using the equation for kinetic energy:

The kinetic energy of the block at the instant after the bullet passes through it is 1000 J

Explanation:

Given:

mass of bullet = m = 20 g = 20x10³ kg

initial velocity = u₁ = 350 m/s

final velocity = u₂ = 150 m/s

The loss in kinetic energy is

quantum mechanics or quantum physics is physics of very small objects (particles) and physical entities.

quantum physics has some parallels to our macro world and some pretty unique ideas which theoretically and mathematically proven to be true even though we will never be able to access them because of our size.

there are many types of particles: subatomic, elementary etc.

subatomic means they are smaller than atom, elementary means they are at the very basis of everything.

subatomic particles are for eg. protons, neutrons but not electrons.

elementary particles are categorised into 3 groups by what they do.

these 3 groups are quarks, leptons and bosons.

light for example is a particle more precisely a photon a part of leptons.

proton (subatomic particle) is made out of 2 up quarks and 1 down quark each of these has a fractional charge like . (i crazy)

most famous scientist who contributed to this physics are:

the topic itself us understand a lot and will probably be vastly used in the future (quantum computers, understanding the big bang,

we also must not forget quantum effects like:

and there is more. but probably too much for this answer to be consistent due to my average understanding of this topic.

hope this you understand quantum mechanics a little more. i'm not an expert in the topic (so don't be like wth if you are an expert) but i'm very interested in it.

anyways quantum physics is a very hard topic (harder than physics (perhaps)) therefore searching for every information there is about it and learning it is unfortunately impossible (you can only specialise into 1 - 3 things or more (perhaps

have fun and i wish you luck!

r3t40

depends on what you mean by "group." for order, it would be coleoptera (beetles). for class, it would be insecta (insects). for phylum, it would be the arthropoda (animals with jointed exoskeletons).

explanation: