Physics, 31.03.2020 00:53 klu65

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

Answers: 3

Show answers

Answers

Answer from: robertotugalanp1wlgs

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:

p_f=p_i

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:

$p_{bf}+p_{wf}=p_{bi}+p_{wi}$

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

$m_bv_{bf}+m_wv_{wf}=m_bv_{bi}+m_wv_{wi}$

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:

$m_bv_{bf}+m_wv_{wf}=m_bv_{bi}$

Solving the equation for the final velocity of the block:

$v_{wf}=\frac{m_bv_{bi} - m_bv_{bf}}{m_w}=\frac{m_b(v_{bi} - v_{bf})}{m_w}$

$v_{wf}=\frac{0.02(350- 150)}{0.75} =5.33 \frac{m}{s}$

(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:

$K=\frac{m_wv_{wf}^2}{2}=\frac{(0.75)(5.33)^2}{2}$

K=10.65 J

Answer from: lufung8627

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

$E_{K} =\frac{1}{2} m(u_{2}^{2} -u_{1} ^{2} )=\frac{1}{2} *20x10^{-3} (350^{2} -150^{2} )=1000J$

Answer from: Quest

it should be -8.6 cm hope this out

Answer from: Quest

are there answer choices to this question? this seems like a question where you have options to choose from.

Another question on Physics

Physics, 21.06.2019 15:00

The optimistic view of human nature held by supporters of the humanistic perspective led to more positive views of human nature throughout the field of psychology.t or f?

Answers: 2

Answer

Physics, 22.06.2019 10:30

Aparticle moves in the xy plane with constant acceleration. at time zero, the particle is at x = 6 m, y = 8.5 m, and has velocity ~vo = (9 m/s) ˆı + (−2.5 m/s) ˆ . the acceleration is given by ~a = (4.5 m/s 2 ) ˆı + (3 m/s 2 ) ˆ . what is the x component of velocity after 3.5 s? answer in units of m/s.

Answers: 1

Answer

Physics, 22.06.2019 12:20

What is the coefficient of kinetic friction μk between the block and the tabletop?

Answers: 1

Answer

Physics, 22.06.2019 12:30

What would be the strength of earth's gravitational field at a point where an 80.0 kg astronaut would experience a 80% reduction in weight

Answers: 3

Answer

You know the right answer?

A 20 gram bullet, traveling horizontally with a velocity of magnitude 350 m/s, is fired into a woode...