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3 years ago

8

2. (Free-fall problem) A ball is thrown up in the air. 10 seconds later it reaches the top of its trajectory. What was the origi

nal velocity it was thrown upward with?

1 answer:

Sever21 [200]3 years ago

8 0

Explanation:

Using kinematics,

t = 10s

v = 0m/s

a = -9.8m/s^2

Therefore u = v - at = 0 - (-9.8)(10) = 98m/s.

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Gamma rays can cause cancer, but they can also be used to treat cancer. How

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Answer:

I think it depends on the purpose of using Gamma rays. It can be both good and bad

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2 years ago

What is hydrometer? Describe its use and any one type of hydrometer.

nexus9112 [7]

Answer:

An instrument for measuring the density of liquids.

Explanation:

A hydrometer is an instrument used to determine specific gravity. It operates based on the Archimedes principle that a solid body displaces its own weight within a liquid in which it floats. Hydrometers can be divided into two general classes: liquids heavier than water and liquids lighter than water.

Thermohydrometers is one type of hydrometer.

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3 years ago

Energy of a SpacecraftVery far from earth(at R=\infty), a spacecraft has run out of fuel and its kineticenergy is zero. If only

Firdavs [7]

Answer:

$s_e=\sqrt{\frac{2GM_e}{R_e^2}}$

Explanation:

In this case mechanical energy is conserved, which means that the sum of the initial kinetic energy and initial potential gravitational energy will be equal to the sum of the final kinetic energy and final potential gravitational energy:

$K_i+U_i=K_f+U_f$

Which in our case will be:

$\frac{mv_i^2}{2}+\frac{-GM_em}{r_i^2}=\frac{mv_f^2}{2}+\frac{-GM_em}{r_f^2}$

Which, since $v_i=0m/s$ , $r_i=infinity$ , $r_f=R_e$ , $v_f=s_e$ and canceling <em>m</em> means that:

$\frac{s_f^2}{2}=\frac{GM_e}{R_e^2}$

Solving for the final velocity we get:

$s_e=\sqrt{\frac{2GM_e}{R_e^2}}$

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3 years ago

use the general formulas for gravitational force and centripetal force to derive the relationship between speed and orbital radi

MrRissso [65]

Answer:

$v = \sqrt{\frac{GM}{r}}$

Explanation:

The universal law of gravitation is defined as:

$F = G\frac{Mm}{r^{2}}$ (1)

Where G is the gravitational constant, M and m are the masses of the two objects and r is the distance between them.

The centripetal force can be found by means of Newton's second law:

$F = ma$ (2)

Since it is a circular motion, the acceleration can be defined as:

$a = \frac{v^{2}}{r}$ (3)

Where v is the velocity and r is the orbital radius.

Replacing equation (3) in equation (2) it is gotten:

$F = m\frac{v^{2}}{r}$ (4)

Hence,

$m\frac{v^{2}}{r} = G\frac{Mm}{r^{2}}$

Then, v can be isolated:

$mv^{2} = G\frac{Mmr}{r^{2}}$

$mv^{2} = G\frac{Mm}{r}$

$v^{2} = G\frac{Mm}{mr}$

$v^{2} = \frac{GM}{r}$

$v = \sqrt{\frac{GM}{r}}$

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3 years ago

Which of the following is not physically possible?

nikklg [1K]

Answer:

(a) -550 °F

Explanation:

No temperature below absolute zero is possible.

Absolute zero on the Fahrenheit scale is -459.67 °F. A temperature of -550 °F is less than that, so is not physically possible.

6 0

2 years ago