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3 years ago

15

if the centripetal acceleration is directed towards the center of the circle at any moment ,the force also must be directed towa

rds the center of the circle .is this statement is true or false

1 answer:

olganol [36]3 years ago

4 0

Answer:

True

Explanation:

The centripetal force is directed towards the center of the circle at any moment. Also, the acceleration.

Centripetal force is a force needed to keep an object along the curved path of a circular body.
A motion in a curved path requires a force directed towards to center to keep it.
A constant force is require to maintain the acceleration of a body along this path.

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A capacitor stores 7.77 x 10-7 J of

Lubov Fominskaja [6]

Answer: $36.22\ V$

Explanation:

Given

Energy in a capacitor $E=7.77\times 10^{-7}\ J$

Charge $Q=4.29\times 10^{-8}\ C$

Energy of a capacitor is given by

$E=\dfrac{1}{2}CV^2=\dfrac{1}{2}QV\quad [\text{Q=CV}]$

Insert the values

$E=\dfrac{1}{2}QV\\\\\Rightarrow 7.77\times 10^{-7}=\dfrac{1}{2}\times 4.29\times 10^{-8}\times V\\\\\Rightarrow V=3.622\times 10\\\\\Rightarrow V=36.22\ V$

Thus, the voltage around the capacitor is $36.22\ V$

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3 years ago

Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thu

Tasya [4]

Answer:

Lightning is seen earlier than the thunder because speed of light is more than the speed of sound. Therefore, even though both occurs as same time and place in the sky, lightning is seen earlier.

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3 years ago

Explain: Is it possible to convert milliliters to liters? How about milliliters to grams?

Advocard [28]

Answer:

yes, it is possible

Explanation:

To convert milliliters to liters, we divide by 1000.

To convert milliliters to grams, we multiply the volume (in ml) by the density (in g).

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3 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:

a)

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.

b)

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:

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

c)

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

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

d)

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.

e)

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:

brainly.com/question/6536722

brainly.com/question/1198647

brainly.com/question/10770261

#LearnwithBrainly

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4 years ago

What does Newton's third law describe?

Dennis_Churaev [7]

A. Equal and opposite forces

Explanation:
History law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exert an equal and opposite force on object A

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3 years ago