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3 years ago

Which statement about subatomic particles is not true?

Physics

2 answers:

Tresset [83]3 years ago

7 0

Answer:

B. is the right answer

Goryan [66]3 years ago

3 0

A) True. protons and neutrons have almost the same mass.

B) Not true. Booo ! protons and neutrons have the same charge.

C) True. unlike protons and electrons neutrons have no charge.

D) True. protons and electrons have opposite charges.

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A cross-country skier can complete a 7. 5 km race in 45 min. What is the skier’s average speed? km/h.

never [62]

The average speed is a scalar quantity. The average speed of the skier is 10 km/hrs.

<h3>What is the average speed?</h3>

It is calculated by dividing the total distance by the total time elapsed.

The

$\overline{v}={\frac{\Delta x}{\Delta t}}$

Where,

$\overline{v}$ = average velocity

${\Delta x}$ = displacement = 7.5 km

${\Delta t}$ = change in time = 45 min = 0.75 hours

Put the values in the formula,

$\overline{v}={\frac{7.5 }{0.75 }}\\\\\overline{v}= 10 \rm \ km/hrs$

Therefore, the average speed of the skier is 10 km/hrs.

Learn more about average speed:

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8 0

3 years ago

Two very small spheres are initially neutral and separated by a distance of 0.30 m. Suppose that 2.50 1013 electrons are removed

quester [9]

Answer:

F = - 1,598 10⁻³ N

Explanation:

Electic strength is given by Coulomb's law

F = k q₁ q₂ / r²

Where k is the Coulomb constant that is worth 8.99 10⁸ N m²/C², q₁ and q₂ are the charges and r is the distance that separates the electric charges

In this case the charge of the two spheres is the same and of a different sign since when you remove the charge of a sphere that was initially neutral, it is left with that charge removed but of the opposite sign

q₁ = q₂ = 2.50 10¹³ electrons = 2.50 10¹³ 1.6 10⁻¹⁹

q₀ = 4.0 10⁻⁶ C

Let's calculate

F = - 8.99 10⁸ (4.0 10⁻⁶)² / 0.30²

F = - 1,598 10⁻³ N

4 0

4 years ago

An attacker at the base of a castle wall 3.65 m high throws a rock straight up with speed 7.4m/s from a height of 1.55m above th

Natali5045456 [20]

a) Yes, the rock will reach the top

b) The final speed is 3.7 m/s

c) The change in speed is 2.4 m/s

d) The change in speed in the two situations do not agree

e) Because the kinetic energy depends quadratically on the speed, $K\propto v^2$

Explanation:

The mechanical energy of the rock at the moment it is thrown from the ground is equal to the sum of its kinetic energy and its potential energy:

$E=KE_i + PE_i = \frac{1}{2}mu^2 + mgh_i$

where

m is the mass of the rock

u = 7.4 m/s is the inital speed

$g=9.8 m/s^2$ is the acceleration of gravity

$h_i = 1.55 m$ is the initial height of the rock

Substituting, we find the initial mechanical energy of the rock

$E=\frac{1}{2}m(7.4)^2 + m(9.8)(1.55)=42.6m$ [J]

In order to reach the top of the castle, the rock should have a mechanical energy of at least

$E' = mgh'$

where

h' = 3.65 m is the heigth of the top

Substituting,

$E'=m(9.8)(3.65)=35.6m$ [J]

Since E > E', it means that the rock has enough mechanical energy to reach the top.

The final mechanical energy of the rock at the top is

$E=mgh'+ \frac{1}{2}mv^2$ (1)

where:

v is the final speed of the rock at the top

Since the mechanical energy is conserved, this should be equal to the initial mechanical energy:

$E=42.6 m$ [J] (2)

Therefore, equating (1) and (2), we can find the final speed of the rock:

$mgh' + \frac{1}{2}mv^2 = 42.6m\\v=\sqrt{2(42.6-gh')}=\sqrt{2(42.6-(9.8)(3.65))}=3.7 m/s$

Since the motion of the rock is a free fall motion (constant acceleration equal to the acceleration of gravity), we can use the following suvat equation:

$v^2 - u^2 = 2as$

where

v is the final speed, at the bottom

u = 7.4 m/s is the initial speed of the rock, at the top

$a=9.8 m/s^2$ is the acceleration of gravity

s = 3.65 - 1.55 = 2.1 m is the vertical displacement of the rock

Solving for v, we find the final speed:

$v=\sqrt{u^2+2as}=\sqrt{7.4^2 + 2(9.8)(2.1)}=9.8 m/s$

Therefore, the change in speed is

$\Delta v = v-u = 9.8 - 7.4 =2.4 m/s$

In the first situation (rock thrown upward), we have:

u = 7.4 m/s (initial speed)

v = 3.7 m/s (final speed)

So the change in speed is

$\Delta v = v-u =3.7 - 7.4 = -3.7 m/s$

While the change in speed in the second situation (rock thrown downward) is

$\Delta v = 2.4 m/s$

Therefore, we see that their magnitudes do not agree.

In both situations, the change in kinetic energy of the rock is equal in magnitude to the change in gravitational potential energy, since the total mechanical energy is conserved.

The change in gravitational potential energy in the two situations is the same (because the change in height is the same), therefore the change in kinetic energy in the two situations is also the same.

However, the kinetic energy of the rock is not directly proportional to the speed, but to the square of the speed:

$K\propto v^2$

Since the initial speed is the same for both situation (7.4 m/s), but the change in kinetic energy has opposite sign in the two situations (negative when the rock is thrown upward, positive when thrown downward), the situation is not symmetrical, therefore in order to have the same magnitude of change in the kinetic energy, the change in speed must be larger when the kinetic energy involved is lower, so in the first situation.

Learn more about kinetic energy and about potential energy:

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6 0

4 years ago

Definition Electromagnetic Wave

lara31 [8.8K]

Explanation:

Definition of electromagnetic wave. : one of the waves that are propagated by simultaneous periodic variations of electric and magnetic field intensity and that include radio waves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

5 0

4 years ago

A Ferris wheel is turning at a constant speed. The riders are _________________ accelerating.

aivan3 [116]

Answer:

The riders are <u>radially</u> accelerating.

Explanation:

The Ferris wheel is making a circular motion. If it is moving with constant velocity, than the acceleration is

$a_{rad} = \frac{v^2}{R}$

towards the center of the wheel.

So, the riders are subject to a constant and radial acceleration, which is called the centripetal acceleration.

3 0

3 years ago