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jek_recluse [69]

3 years ago

5

The driver then tests the brakes on the car and safely comes to a complete stop with constant acceleration from 26.8 meters per

second in only 32.3 meters.
A. What is the magnitude and direction of the cars acceleration?

B. How much time did the car travel under this constant acceleration before stopping?

1 answer:

Temka [501]3 years ago

5 0

Answer:

62.78

Explanation:

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Arigid body must rotate about an axis in order for it to have angular momentum about that axis. True False

kompoz [17]

Answer:

False

Explanation:

Let's consider the definition of the angular momentum,

$\vec{L} = I \vec{\omega}$

where $I = \int\limits_m r^2 dm = \lim_{n \to \infty} \sum\limits_{i=1}^n m_i r_i^2$ is the moment of inertia for a rigid body. Now, this moment of inertia could change if we change the axis of rotation, because "r" is defined as the distance between the puntual mass and the nearest point on the axis of rotation, but still it's going to have some value. On the other hand,

$\vec{\omega} = \frac{\vec{r} \times \vec{v}}{r^2}$ so $\vec{\omega} \neq 0$ unless $\vec{r}$ ║ $\vec{v}$ .

In conclusion, a rigid body could rotate about certain axis, generating an angular momentum, but if you choose another axis, there could be some parts of the rigid body rotating around the new axis, especially if there is a projection of the old axis in the new one.

7 0

3 years ago

What is one positive outcome of the recent<br>events?

fenix001 [56]

Answer:

Analyze the positive and negative consequences of catastrophic events of the last 40-50 years and the individuals that had an impact on these events. Meaning.

Explanation:

5 0

3 years ago

Read 2 more answers

Tennis balls traveling at greater than 100 mph routinely bounce off tennis rackets. At some sufficiently high speed, however, th

Kipish [7]

Answer:

Probability of tunneling is $10^{- 1.17\times 10^{32}}$

Solution:

As per the question:

Velocity of the tennis ball, v = 120 mph = 54 m/s

Mass of the tennis ball, m = 100 g = 0.1 kg

Thickness of the tennis ball, t = 2.0 mm = $2.0\times 10^{- 3}\ m$

Max velocity of the tennis ball, $v_{m} = 200\ mph$ = 89 m/s

Now,

The maximum kinetic energy of the tennis ball is given by:

$KE = \frac{1}{2}mv_{m}^{2} = \frac{1}{2}\times 0.1\times 89^{2} = 396.05\ J$

Kinetic energy of the tennis ball, KE' = $\frac{1}{2}mv^{2} = 0.5\times 0.1\times 54^{2} = 154.8\ m/s$

Now, the distance the ball can penetrate to is given by:

$\eta = \frac{\bar{h}}{\sqrt{2m(KE - KE')}}$

$\bar{h} = \frac{h}{2\pi} = \frac{6.626\times 10^{- 34}}{2\pi} = 1.0545\times 10^{- 34}\ Js$

Thus

$\eta = \frac{1.0545\times 10^{- 34}}{\sqrt{2\times 0.1(396.05 - 154.8)}}$

$\eta = \frac{1.0545\times 10^{- 34}}{\sqrt{2\times 0.1(396.05 - 154.8)}}$

$\eta = 1.52\times 10^{-35}\ m$

Now,

We can calculate the tunneling probability as:

$P(t) = e^{\frac{- 2t}{\eta}}$

$P(t) = e^{\frac{- 2\times 2.0\times 10^{- 3}}{1.52\times 10^{-35}}} = e^{-2.63\times 10^{32}}$

$P(t) = e^{-2.63\times 10^{32}}$

Taking log on both the sides:

$logP(t) = -2.63\times 10^{32} loge$

$P(t) = 10^{- 1.17\times 10^{32}}$

6 0

3 years ago

Two marbles, one twice as heavy as the other, are dropped to the ground from the roof of a building. Just before hitting the gro

Andreyy89

Answer:

B. twice as much kinetic energy

Explanation:

Lets take the mass of the first marble =2 m

the mass of the second marble = m

We know that velocity of particle does not depends on their mass that is the velocity of both mass will be same after dropping from the roof.

We know that kinetic energy of a mass is given as

$KE=\dfrac{1}{2}Mv^2$

Kinetic energy for heavier mass

$KE=\dfrac{1}{2}\times 2m\times V^2$

Kinetic energy for light mass

$KE'=\dfrac{1}{2}\times m\times V^2$

KE=2 KE '

Form above two equation we can say that ,the kinetic energy for the heavier mass is twice the lighter mass.

Therefore the answer will be B.

7 0

3 years ago

Science please helppp

Daniel [21]

The red box must way more. Gravitational potential energy is the product of a an objects mass times the acceleration due to gravity (which is constant on earth) times its height. Since the objects are on the same shelf they are at the same height, and since gravitational acceleration is constant as long as we stay on planet earth, then the mass is the only possible thing that could have changed. This means that the red box must weigh more than the blue box.

3 0

3 years ago