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3 years ago

5

A student throws a 0.22 kg rock horizontally at 20.0 m/s from 10.0 m above the ground. Find the initial kinetic energy of the ro

ck.

1 answer:

LekaFEV [45]3 years ago

6 0

Answer:

44J

Explanation:

Given parameters:

Mass of rock = 0.22kg

Initial velocity = 20m/s

Distance moved = 10m

Unknown:

Initial kinetic energy of the rock = ?

Solution:

To solve this problem, we need to understand that kinetic energy is the energy due to the motion of a body.

It is mathematically expressed as;

Kinetic energy = $\frac{1}{2}$ m v²

m is the mass

v is the velocity

Kinetic energy = $\frac{1}{2}$ x 0.22 x 20² = 44J

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The momentum of an electron is 1.75 times larger than the value computed non-relativistically. What is the speed of the electron

FrozenT [24]

Answer:

<em>Speed of the electron is 2.46 x 10^8 m/s</em>

<em></em>

Explanation:

momentum of the electron before relativistic effect = $M_{0} V$

where $M_{0}$ is the rest mass of the electron

V is the velocity of the electron.

under relativistic effect, the mass increases.

under relativistic effect, the new mass M will be

M = $M_{0}/ \sqrt{1 - \beta ^{2} }$

where

$\beta = V/c$

c is the speed of light = 3 x 10^8 m/s

V is the speed with which the electron travels.

The new momentum will therefore be

==> $M_{0}V/ \sqrt{1 - \beta ^{2} }$

It is stated that the relativistic momentum is 1.75 times the non-relativistic momentum. Equating, we have

1.75 $M_{0} V$ = $M_{0}V/ \sqrt{1 - \beta ^{2} }$

the equation reduces to

1.75 = $1/ \sqrt{1 - \beta ^{2} }$

square both sides of the equation, we have

3.0625 = 1/ $(1 - \beta ^{2} )$

3.0625 - 3.0625 $\beta ^{2}$ = 1

2.0625 = 3.0625 $\beta ^{2}$

$\beta ^{2}$ = 0.67

β = 0.819

substitute for $\beta = V/c$

V/c = 0.819

V = c x 0.819

V = 3 x 10^8 x 0.819 = <em>2.46 x 10^8 m/s</em>

6 0

4 years ago

A sound-producing object is moving toward an observer. The sound the observer hears will have a frequency ___ that actually bein

Readme [11.4K]

The answer is <span>higher than.
</span><span>A sound-producing object is moving toward an observer. The sound the observer hears will have a frequency higher than that actually being produced by the object.

Why?
</span>As the source of the waves is moving toward the observer, each of the successive wave crest<span> is emitted from a position closer to the observer than the previous wave.
Thus each wave takes slightly less time to reach the observer than the previous wave. So, the time between the arrival of successive wave crests at the observer is reduced, increasing the frequency. </span>

5 0

4 years ago

Read 2 more answers

A ball is thrown horizontally from the top of a building 54 m high. The ball strikes the ground at a point 35 m horizontally awa

Ivanshal [37]

Answer:

V=34.2 m/s

Explanation:

Given that

Height , h= 54 m

Horizontal distance , x = 35 m

Given that , the ball is thrown horizontally , therefore the initial vertical velocity will be zero.

In vertical direction :

We know that

$V^2_y=U^2_y+2 g h$

Now by putting the values in the above equation we got

$V^2_y=U^2_y+2 g h$

$V^2_y=0^2+2\times 9.81 \times 54$

Assume $g= 9.81 m/s^2$

Thus

$V^2_y=1059.48$

$V_y=\sqrt{1059.48}\ m/s$

$V_y=32.54 m/s$

We also know that

$V_y=U_y+ g\times t$

$32.54=9.81\times t$

$t=\dfrac{32.54}{9.81}=3.31\ s$

In horizontal direction :

$x=U_x\times t$

$U_x=\dfrac{35}{3.31}=10.54\ m/s$

Thus the resultant velocity

$V=\sqrt{V^2_y+U^2_x}$

$V=\sqrt{32.54^2+10.54^2}=34.2\ m/s$

V=34.2 m/s

Therefore the velocity will be 34.2 m/s.

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4 years ago

Is a solid PETROLEM

bearhunter [10]

No petroleum is a liquid

3 0

3 years ago

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A person is standing on a level floor. His head, upper

BabaBlast [244]

Answer:

$y_{cg} = 1.03 m$

Explanation:

Given data:

weigh (head+arms + head) w_1 = 438 N

centre of gravity y_1= 1.28 m

weigh (upper leg) w_2 = 144 N

Center of gravity y_2 = 0.760 m

weigh ( lower leg + feet) = 87 N

centre of gravity = y_3 = 0.250 m

location of center of gravity $= \frac{w_1 y_1 + w_2 y_2 + w_3 y_3}{w_1 +W_2 +w_3}$

$y_{cg} = \frac{438 \times 1.28 + 144\times 0.760 + 87 \times 0.250}{438+144+87}$

$y_{cg} = 1.03 m$

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4 years ago