What is a rock that is full of tiny connected air spaces

Explain how gravity and friction work to slow down a kicked soccer ball.

goblinko [34]

Use your feet to stop it since it is soccer you can't use your hands!!!! P.S. you can't use gravity.

5 0

3 years ago

Can anyone help?6th question.free brainliest answer...

DIA [1.3K]

There's a crest and a trough in each complete wave. So the question is describing 10 complete waves.

After that, the question becomes somewhat murky. It goes on to say "its time period is 0.2 seconds".

-- The "time period" of a wave is usually defined as the time for one complete wave. If that's what the phrase means, then ...

Frequency = ( 1/0.2sec )

Frequency = 5 Hz.

= = = = = = = = = =

BUT ... Is the question awkwardly trying to tell us that the 10 waves take 0.2 seconds ? If that's what it's saying, then ...

Frequency = (10) / (0.2 sec)

Frequency = 50 Hz .

6 0

3 years ago

The flywheel of a steam engine runs with a constant angular velocity of 190 rev/min. When steam is shut off, the friction of the

Ivanshal [37]

Answer:

(a) $\alpha = - 1.32\ rev/m^{2}$

(b) $\theta = 13674\ rev$

(c) $\alpha_{tan} = 8.75\times 10^{- 4}\ m/s^{2}$

(d) $a = 22.458\ m/s^{2}$

Solution:

As per the question:

Angular velocity, $\omega = 190\ rev/min$

Time taken by the wheel to stop, t = 2.4 h = $2.4\times 60 = 144\ min$

Distance from the axis, R = 38 cm = 0.38 m

Now,

(a) To calculate the constant angular velocity, suing Kinematic eqn for rotational motion:

$\omega' = \omega + \alpha t$

$omega'$ = final angular velocity

$\omega$ = initial angular velocity

$\alpha$ = angular acceleration

Now,

$0 = 190 + \alpha \times 144$

$\alpha = - 1.32\ rev/m^{2}$

Now,

(b) The no. of revolutions is given by:

$\omega'^{2} = \omega^{2} + 2\alpha \theta$

$0 = 190^{2} + 2\times (- 1.32) \theta$

$\theta = 13674\ rev$

(c) Tangential component does not depend on instantaneous angular velocity but depends on radius and angular acceleration:

$\alpha_{tan} = 0.38\times 1.32\times \frac{2\pi}{3600} = 8.75\times 10^{- 4}\ m/s^{2}$

(d) The radial acceleration is given by:

$\alpha_{R} = R\omega^{2} = 0.32(80\times \frac{2\pi}{60})^{2} = 22.45\ rad/s$

Linear acceleration is given by:

$a = \sqrt{\alpha_{R}^{2} + \alpha_{tan}^{2}}$

$a = \sqrt{22.45^{2} + (8.75\times 10^{- 4})^{2}} = 22.458\ m/s^{2}$

5 0

3 years ago

Betty weighs 420 n and she is sitting on a playground swing seat that hangs 0.40 m above the ground. tom pulls the swing back an

Svet_ta [14]

Weight = mass * gravity
420 = mass * 9.8
mass of Betty = 42.857 kg

Difference in height = 1 - 0.45 = 0.55 meters

Total energy = Kinetic energy + potential energy

At the highest point, the kinetic energy is zero while the potential energy is maximum, therefore, we can get the total energy as follows:
Total energy = 0 + mgh
Total energy = 42.857*9.8*0.55 = 231 Joules

At the lowest point, the potential energy is zero while the kinetic energy is maximum. Therefore:
Total energy = 0.5 * m * (v)^2 + 0
231 = 0.5 * (42.857) * (velocity)^2
(velocity)^2 = 10.78
velocity = 3.28 meters/sec

8 0

4 years ago

This graph is accurate because A) mechanical waves cannot travel through a medium. B) electromagnetic waves cannot travel throug

il63 [147K]

Answer:

IT would be C.electromagnetic waves move faster than mechanical waves.

Explanation:

4 0

3 years ago

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