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2 years ago

10

in an effort to reach the store before it closed the motorist increase the speed of his car from 20 m per second to 60 meters pe

r second over a four second. What was the car's acceleration

1 answer:

Ber [7]2 years ago

7 0

Answer:

10

Explanation:

Givens

vi = 20 m/s

vf = 60 m/s

t = 4 second.

Formula

a = (vf - vi) / t

a = (60 - 20)/4

a = 40 / 4

a = 10 m/s^2

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Which phrase describes an electromagnetic wave

Viefleur [7K]

Answer:

<u>a transverse wave consisting of changing electric fields and changing magnetic fields.</u>

Explanation:

An electromagnetic wave is a wave generated by the vibration of perpendicular electric and magnetic fields, which may progate through vacuum (empty space) or a material medium.

All electromagnetic waves propagate at the same speed in vacuum. This speed is approximately 3.0 × 10⁸ m/s. Which is generally referred as the speed of light, but it is the same constant speed of any electromagnetic wave in the vacuum, c.

In general, waves transfer energy when they travel, but only electromagnetic waves can travel in vacuum. The waves that cannot travel in vacuum are named mechanical waves (they need a medium to travel).

There are two types of waves depending on how they propagate: transverse waves and longitudinal waves. The transverse waves travel perperdiculary to the direcction of the vibration, while longitudinal waves travel parallel to the direction of the vibration.

The classical example of transverse waves is a rope that oscilates up and down. The classical example of longitudinal waves is a spring that you pull and push by an end and so it moves forward and back. Sound is also a longitudinal wave.

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2 years ago

It is known that the gravitational force of attraction between two alpha particles is much weaker than the electrical repulsion.

natali 33 [55]

Answer:

<em>The ratio of gravitational force to electrical force is 3.19 x 10^-36 </em>

<em></em>

Explanation:

mass of an alpha particle = 6.64 x $10^{-27}$ kg

charge on an alpha particle = +2e = +2(1.6 x $10^{-19}$ C) = 3.2 x $10^{-19}$ C

distance between particles = d

For gravitational attraction:

The force of gravitational attraction F = $\frac{Gm^{2} }{r^{2} }$

where G = gravitational constant = 6.67 x $10^{-11}$ m^3 kg^-1 s^-2

r = the distance between the particles = d

m = the mass of each particle

therefore, gravitational force = $\frac{6.67*10^{-11}*(6.64*10^{-27} )^{2} }{d^{2} }$ = $\frac{2.94*10^{-63} }{d^{2} }$ Newton

For electrical repulsion:

Electrical force between the particles = $\frac{-kQ^{2} }{r^{2} }$

where k is the Coulomb's constant = 9.0 x $10^{9}$ N•m^2/C^2

r = distance between the particles = d

Q = charge on each particle

therefore, electrical force = $\frac{-9*10^{9}*(3.2*10^{-19} )^{2} }{d^{2} }$ = $\frac{-9.216*10^{-28} }{d^{2} }$ Newton

the negative sign implies that there is a repulsion on the particles due to their like charges.

Ratio of the magnitude of gravitation to electrical force = $\frac{2.94*10^{-63} }{9.216*10^{-28} }$

==> <em>3.19 x 10^-36 </em>

8 0

3 years ago

Jessica has a mass of 55kg she sleds down a hill that has a slope of 32 degrees. what is the component of her weight that is alo

Arturiano [62]

Answer:

W = 285.62 N

Explanation:

It is given that,

Mass of Jessica is 55 kg

Slope of the hill is 32 degrees

We need to find the component of her weight that is along her direction of motion.

The component along her direction of motion is shown in attached figure. It means

$W_y=mg\sin\theta\\\\W_y=55\times 9.8\times \sin(32)\\\\W_y=285.62\ N$

So, the component of her weight that is along her direction of motion is 285.62 N.

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3 years ago

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WARRIOR [948]

The answer is c. the force of his swing

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The force exerted on the ball causes the change of velocity.

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3 years ago

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HACTEHA [7]

Answer: P= mad/t or P=w/t so P= 300/6= 50 W

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3 years ago