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Anvisha [2.4K]
3 years ago
15

A bullet of inertia m traveling at speed v is fired into a wooden block that has inertia 4m and rests on a level surface. The bu

llet passes through the block and emerges with speed v/3, taking a negligible amount of the wood with it. The block moves to the right but comes to rest after traveling a distance d.
What is the magnitude of the frictional force between the block and the surface while the block is moving?


What is the ratio of the energy dissipated as the bullet passes through the block to the energy dissipated by friction between the surface and the bottom face of the block?


I solved the first one and got (4mv^2)/(9d) but it said "your answer either contains an incorrect numerical multiplier or is missing one" so I'm not really sure what I did wrong.
Physics
1 answer:
GREYUIT [131]3 years ago
5 0

Answer:

F = mv²/(18d)

7

Explanation:

Momentum before collision = momentum after collision

mv = m(v/3) + (4m) V

v = v/3 + 4V

4V = 2v/3

V = v/6

The acceleration of the block is:

v² = v₀² + 2aΔx

(0 m/s)² = (v/6)² + 2ad

2ad = -v²/36

a = -v²/(72d)

The friction force is therefore:

∑F = ma

-F = (4m) (-v²/(72d))

F = mv²/(18d)

The energy dissipated during the collision is:

ΔE = 1/2 mv² − (1/2 m(v/3)² + 1/2 (4m)(v/6)²)

ΔE = 1/2 mv² − (1/18 mv² + 1/18 mv²)

ΔE = 1/2 mv² − 1/9 mv²

ΔE = 7/18 mv²

The energy dissipated by the friction force:

W = Fd

W = 1/18 mv²

The ratio is:

ΔE / W

(7/18 mv²) / (1/18 mv²)

7

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The Three fission reactions will produce nine neutrons

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Fission can be defined as a nuclear process that involves the breaking of a whole nuclear matter into smaller bits.

In a fission reaction, the matter is broken down into simpler bits.

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2 years ago
Which statement is false?
Mkey [24]

Answer:

Once you reach adulthood, you will not experience peer pressure.

Explanation:

We tend to believe that self-control comes from within, but many of our attitudes depend as much on friends and family as on ourselves. That's because at any stage of our life (even the adult stage) our friends and our family have the power to influence us, sometimes that influence is good and sometimes bad, it's up to us to reason about them.

The people around us have the power to make us fat, consume more alcohol, worry less about the environment and expose ourselves to the sun without proper protection, among many other things.

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3 0
3 years ago
Read 2 more answers
33 POINTS How can I get the temperature? SOUND SPEED 340 m/s = 331 m/s + (0,6xTemperature)
inessss [21]

(340-331)/0.6 = temp

9/0.6

90/6

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6 0
3 years ago
G a magnetic field perpendicular to the plane of a wire loop is uniform in space but changes with time t in the region of the lo
Luden [163]

Answer:

e = Δφ / Δt     induced emf is proportional to enclosed flux

Also φ  = B * A      flux is proportional to area and enclosed field

If the induced emf e increases with time than the flux and hence the magnetic field is increasing with time  (replace B with G)

Since e = ΔG * A / Δt    if e is linear then G must also be linear and be proportional to the time

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1 year ago
A coaxial cable consists of a solid inner cylindrical conductor of radius 2 mm and an outer cylindrical shell of inner radius 3
4vir4ik [10]

Answer:

d) 1.2 mT

Explanation:

Here we want to find the magnitude of the magnetic field at a distance of 2.5 mm from the axis of the coaxial cable.

First of all, we observe that:

- The internal cylindrical conductor of radius 2 mm can be treated as a conductive wire placed at the axis of the cable, since here we are analyzing the field outside the radius of the conductor. The current flowing in this conductor is

I = 15 A

- The external conductor, of radius between 3 mm and 3.5 mm, does not contribute to the field at r = 2.5 mm, since 2.5 mm is situated before the inner shell of the conductor (at 3 mm).

Therefore, the net magnetic field is just given by the internal conductor. The magnetic field produced by a wire is given by

B=\frac{\mu_0 I}{2\pi r}

where

\mu_0 is the vacuum permeability

I = 15 A is the current in the conductor

r = 2.5 mm = 0.0025 m is the distance from the axis at which we want to calculate the field

Substituting, we find:

B=\frac{(4\pi\cdot 10^{-7})(15)}{2\pi(0.0025)}=1.2\cdot 10^{-3}T = 1.2 mT

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