TRUE OR FALSE The sun has more gravity than the earth because it is more massive.

A stationary 2 kg football is kicked by a footballer, the football moves off with a velocity of 5 m/s. If the footballer is in c

-BARSIC- [3]

Answer:

F = 20 N

Explanation:

Given that,

Mass of the football, m = 2 kg

Initial speed, u = 0

Final speed,v = 5 m/s

The time of contact, t = 0.5 s

We need to found the average force applied by the footballer on the football. We can find it using the formula.

$F=\dfrac{m(v-u)}{t}\\\\F=\dfrac{2\times (5-0)}{0.5}\\\\F=20\ N$

So, the required force is 20 N.

7 0

3 years ago

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During most of its lifetime, s star maintains an equilibrium size in which the inward force of gravity on each atom is balanced

frez [133]

Answer:

$r_f=137493m$

$v=8638940m/s$

Explanation:

During this process the mass $M=2\times10^{30}Kg$ will be considered constant. We start from a radius $r_i=7\times10^8m$ and a period $T_i=30\ days=(30)(24)(60)(60)s=2592000s$ . The final period is $T_f=0.1s$ .

Angular momentum L is conserved in this process. We can use the formula $L=I\omega$ , where I is the momentum of inertia (which for a solid sphere is $I=\frac{2mr^2}{5}$ ) and $\omega=\frac{2\pi }{T}$ is the angular velocity, so we can write the star's angular momentum as:

$L=I\omega=\frac{2mr^2}{5}\frac{2\pi }{T}=\frac{4\pi mr^2 }{5T}$

Since $L_f=L_i$ we have:

$\frac{4\pi mr_f^2 }{5T_f}=\frac{4\pi mr_i^2 }{5T_i}$

Which can be simplified as:

$\frac{r_f^2 }{T_f}=\frac{r_i^2 }{T_i}$

Which means:

$r_f=\sqrt{\frac{r_i^2 T_f}{T_i}}=r_i \sqrt{\frac{T_f}{T_i}}$

Which for our values is:

$r_f=r_i \sqrt{\frac{T_f}{T_i}}=(7\times10^8m) \sqrt{\frac{0.1s}{2592000s}}=137493m$

And we calculate the speed of a point on the equator by dividing the final circumference over the final period:

$v=\frac{C_f}{T_f}=\frac{2\pi r_f}{T_f}=\frac{2\pi (137493m)}{(0.1s)}=8638940m/s$

3 0

4 years ago

SOMEONE PLEASE HELP!!!! Select the correct answer. Which planet is planet A

AURORKA [14]

Saturn is the answer

4 0

4 years ago

3.

alexandr402 [8]

Answer:

1.92 m/s

Explanation:

Velocity is defined as the distance moved per unit time with consideration of the direction. The direction aspect differentiates speed from velocity since for speed, we don't need to consider the direction.

$v=\frac {d}{t}$

Distance moved for circular path is equal to its circumference and the circumference is given by $2\pi r$ where r is the radius and substituting $2\pi r$ for d then

$v=\frac {2\pi r}{t}$

Substituting 5.5 m for r and 18 s for t then

$v=\frac {2\pi \times 5.5}{18}=1.919862177 m/s\approx 1.92 m/s$

To the nearest hundredth, the velocity is 1.92 m/s

4 0

4 years ago

Which statement describes the use of control rods?

Anit [1.1K]

Control rods are rods, plates, or tubes containing a neutron absorbing material (material with high absorbtion cross-section for thermal neutron) such as boron, hafnium, cadmium, etc., used to control the power of a nuclear reactor.
so the statement that describe a control rod is:
Control rods are lowered into the reactor to slow down the reaction by absorbing neutrons.

6 0

4 years ago

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