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4 years ago

If a Girl Bounces a Ball, At what point does the ball have velocity?

Physics

1 answer:

mihalych1998 [28]4 years ago

5 0

An object ALWAYS has velocity, although the velocity may be zero for most of the time, or even all the time.

'Velocity' means the object's speed AND the direction in which it's moving.

As long as the girl stands and holds the ball in her hand, the ball's velocity is zero. As soon as she drops it out of her hand, it starts having velocity that's not zero.

While it's bouncing, its velocity is . . .

== growing and downward while it's falling from her hand toward the ground,

== zero for the instant of time when it hits the ground and changes direction from down to up,

== shrinking and upward while it's rising from the ground to her hand,

== zero for the instant of time when it hits her hand and changes direction from up to down.

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A thin, uniform metal bar, 2.00 m long and weighing 90.0 N, is hanging vertically from the ceiling by a frictionless pivot. Sudd

matrenka [14]

Answer:

(a) The "angular speed" is 5.88 rad/s.

Explanation:

Given values,

The length of the bar is L = 2m

The weight of the bar is w = 90 N

The metal bar is hanging vertically from the ceiling by a frictionless pivot

The mass of the ball is m = 3kg

The distance between the ceiling and the ball is d = 1.5m

$\text { The "initial speed of the ball" is } V_{i}=10 \mathrm{m} / \mathrm{s}$

$\text { The "final speed of the ball" is } V_{f}=6 \mathrm{m} / \mathrm{s}$

(a) Calculating the angular speed:

$W_{\mathrm{f}}=\left(3 \mathrm{mg} \mathrm{d} \frac{V_{i}+V_{f}}{w l^{2}}\right)$

$W_{f}=\left(3 \times 3 \times 9.8 \times 1.5 \times \frac{10+6}{90 \times 2^{2}}\right)$

$W_{f}=\frac{2116.8}{360}$

$\mathrm{W}_{\mathrm{f}}=5.88 \mathrm{rad} / \mathrm{s}$

The angular speed is 5.88 rad/s.

(b) The "angular momentum" is conserved because the torque is not exerted by "the pivot" on the system about the "axis of rotation" but the "linear momentum" is not conserved because "the pivot" exerts a "vertical" and a "horizontal force" on the system during the collision.

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4 years ago

What is the definition of physical weathering?

jeyben [28]

Answer rocks, soil and minerals being slowly broken down or broken apart by the Earth's environment such as pressure, temperature, water and ice

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4 years ago

A stone falls from rest from the top of a cliff. A second stone is thrown downward from the same height 2.7 s later with an init

Darina [25.2K]

Answer:4.05 s

Explanation:

Given

First stone is drop from cliff and second stone is thrown with a speed of 52.92 m/s after 2.7 s

Both hit the ground at the same time

Let h be the height of cliff and it reaches after time t

$h=\frac{gt^2}{2}$

For second stone

$h=52.92\times \left ( t-2.7\right )+\frac{g\left ( t-2.7\right )^2}{2}$ ---2

Equating 1 &2 we get

$\frac{gt^2}{2}=52.92\times \left ( t-2.7\right )+\frac{g\left ( t-2.7\right )^2}{2}$

$\frac{g}{2}\left ( t-t+2.7\right )\left ( 2t-2.7\right )-\left ( t-2.7\right )52.92=0$

$13.23\times \left ( 2t-2.7\right )-\left ( t-2.7\right )52.92=0$

$26.46t-35.721-52.92t+142.884=0$

$t=4.05 s$

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3 years ago

A sample of a substance has a high density, yet a low particle motion. This sample must be a

avanturin [10]

The most possible answer is letter B) Liquid.
If we are going to base the answer to the motion of particles, liquid is the best answer since solid's particle cannot move for they are tightly packed while the particles of gas and plasma (ionized gas) are free and move at high speeds.

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3 years ago

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Which of these should be avoided in order to prevent heart diseases and disorders?

White raven [17]

Answer:

drugs and alcohol

Explanation:

All the others will help your body, while drugs and alcohol will only harm it .

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3 years ago

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