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belka [17]
3 years ago
13

Neglecting air, what speed does a rock thrown straight up have to be to reach the edge of our atmosphere: say 100 km? Still negl

ecting air, after the rock falls back down, what speed will it have just before it hits the earth? Assume constant gravity g = 10 m/s 2 for earth’s gravity.
Physics
1 answer:
Ugo [173]3 years ago
5 0

To solve this problem it is necessary to apply the kinematic equations of movement description, specifically those that allow us to find speed and acceleration as a function of distance and not time.

Mathematically we have to

v_f^2-v_i^2 = 2ax

Where,

v_{f,i} = Final velocity and Initial velocity

a = Acceleration

x = Displacement

From the description given there is no final speed (since it reaches the maximum point) but there is a required initial speed that is contingent on traveling a certain distance under the effects of gravity

0 - v_i^2 = 2(9.8)(100*10^3)

v_i = 14*10^2m/s

Therefore the speed which must a rock thrown straight up is 14*10^2m/s to reach the edge of our atmosphere.

The displacement and gravity traveled are the same, therefore the final speed will be the same but in the opposite vector direction (towards the earth), that is 14 * 10 ^ 2m / s

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If it requires 7.0 j of work to stretch a particular spring by 2.1 cm from its equilibrium length, how much more work will be re
SVEN [57.7K]
4.6 j more. To get this take 7 and multiply it by 3.5 to get 24.5 take the x which is what you’re looking for and multiply it by the 2.1 to get 2.1x. Take 24.5 and divide it by 2.1 x and get 11.6. Subtract 11.6 by 7 and get 4.6
8 0
3 years ago
A composite material is to be designed with epoxy (Em 3.5 GPa) and unidirectional fibers. The longitudinal elastic modulus of th
LenKa [72]

Answer:

Minimum elastic modulus of fiber = 455.64 GPa

Explanation:

Contents of composite material = Epoxy and Unidirectional fibers

Elastic modulus of epoxy = 3.5 GPa

Elastic modulus of composite material = 320 GPa

Volume fraction of fiber = 70 %

Volume fraction of epoxy = 100 - 70 = 30%

Elastic modulus of composite material = 3.5 x 0.3 + Elastic modulus of fiber x 0.7 = 320

0.7 x Elastic modulus of fiber = 320 - 1.05 = 318.95

Elastic modulus of fiber = 455.64 GPa

Minimum elastic modulus of fiber = 455.64 GPa

5 0
3 years ago
A transformer consists of 290 primary windings and 824 secondary windings. Part A: If the potential difference across the primar
jasenka [17]

Answer:

Part 1) Voltage in secondary windings is 61.08 Volts

Part 2) Current in secondary windings is 0.53 Amperes

Explanation:

The potential developed in the primary and secondary winding of a transformer are related as

\frac{N_{p}}{N_{s}}=\frac{V_{p}}{V_{s}}

where

Np no of turns in primary coil

Ns no of turns in secondary coil

Vp Voltage of turns in primary coil

Vs Voltage of turns in secondary coil

Applying values in the formula we get

\frac{290}{824}=\frac{21.5}{V_{s}}\\\\\therefore V_{s}=21.5\times \frac{824}{290}=61.08V

Part 2)

Using Ohm's law the current is given by

I=\frac{V_{s}}{R}\\\\I=\frac{61.089}{115}=0.53A

5 0
3 years ago
What is Icm, the moment of inertia of the disk around its center of mass? You should know this formula well.
kirill115 [55]

Answer:

I_{cm}=\frac{MR^{2}}{2}

Explanation:

First at all let's understand what is moment of inertia (I). The moment of inertia of a body is the rotational analog of mass in linear motion, this is, it determines the force we should apply to the body to acquire a specific angular acceleration. But in the rotational case we should specify about what point we are going to rotate an object so always the moment of inertia is defined respect to an arbitrary axis. It's usual to use the center of mass as an axis of rotation, because it's an unique point where we can assume all the mass of the object is concentrated.The moment of inertia respect of an axis that passes through the center of mass is denoted I_{cm}.

Now, if the disk you're talking about has uniform density the center of mass is exactly at the geometrical center of the disk, and the moment of inertia of a disk as that is:

I_{cm}=\frac{MR^{2}}{2}

6 0
3 years ago
Electrons returning to the ground state from varying excited states always:
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Emit radiation exactly equal in energy, to the energy difference between states.
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3 years ago
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