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3 years ago

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A person throws a ball from height of 6 feet with an initial vertical velocity of 48 feet per second. Use the vertical motion mo

del, h = -16t? + vt +s, where v is the initial velocity in feet per second and s is the height in feet, to calculate the amount of time the ball is in the air before it hits the ground again. Round your answer to the nearest tenth if necessary. Time in air: ___seconds

1 answer:

True [87]3 years ago

7 0

Explanation:

Recall the equation for time is distance divided by speed. Here you can use that to solve for "t".

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g Estimate the number of photons emitted by the Sun in a second. The power output from the Sun is 4 Ã— 1026 W and assume that th

vagabundo [1.1K]

Answer:

The value is $N = 1.107 *10^{45 } \ photons$

Explanation:

From the question we are told that

The power output from the sun is $P_o = 4 * 10^{26} \ W$

The average wavelength of each photon is $\lambda = 550 \ nm = 550 *10^{-9} \ m$

Generally the energy of each photon emitted is mathematically represented as

$E_c = \frac{h * c }{ \lambda }$

Here h is the Plank's constant with value $h = 6.62607015 * 10^{-34} J \cdot s$

c is the speed of light with value $c = 3.0 *10^{8} \ m/s$

So

$E_c = \frac{6.62607015 * 10^{-34} * 3.0 *10^{8} }{ 550 *10^{-9} }$

=> $E_c = 3.614 *10^{-19} \ J$

Generally the number of photons emitted by the Sun in a second is mathematically represented as

$N = \frac{P }{E_c}$

=> $N = \frac{4 * 10^{26} }{3.614 *10^{-19}}$

=> $N = 1.107 *10^{45 } \ photons$

5 0

2 years ago

Which si unit whould be most appropriate for describing the length of a shoe?

aniked [119]

Answer:

Milimeters

Explanation:

This kind of question must be checked with everyday elements, in this way we will analyze each of the options until we reach the appropriate:

kilograms can not be because this unit serves to measure the mass not the length.

kilometers (km) is a unit of length, but however it does not serve for this measurement since a km is equivalent to 1000 meters, therefore measuring the length of a shoe with a ruler measuring 1000 meters is very impractical.

milliliters is a unit of volume, and can often be found in the measurement of volume content of liquids, for example 700 milliliters of milk or 1000 milliliters of water. Therefore it is impractical to measure a shoe with a unit of volume.

In this way the way to measure a shoe correctly is using a ruler or measuring instrument graduated in millimeters.

4 0

3 years ago

A piston-cylinder device contains Helium gas initially at 150 kPa, 20 o C, and 0.5m 3 . The helium is now compressed in a polytr

Molodets [167]

Answer:

Explanation:

Given

$P_1=150 kPa$

$T_1=20^{\circ}C$

$V_1=0.5 m^3$

$T_2=140^{\circ}C$

$P_2=400 kPa$

R for Helium $R=2.076$

$c_v=3.115 kJ/kg-K$

mass of gas $m=\frac{P_1V_1}{RT_1}$

$m=\frac{150\times 0.5}{2.076\times 293}$

$m=0.123 kg$

Similarly $V_2$ can be found

$\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}$

$V_2=0.264 m^3$

Work done $W=\int_{V_1}^{V_2}PdV$

$W=\frac{P_2V_2-P_1V_1}{n-1}$

$W=\frac{mR(T_2_T_1)}{n-1}$

Since it is a polytropic Process

therefore $PV^n=c$

$P_1V_1^n=P_2V_2^n$

$(\frac{V_1}{V_2})^n=\frac{P_2}{P_1}$

$(\frac{0.5}{0.264})^n=\frac{400}{150}$

$n=\frac{\ln 2.66}{\ln 1.893}$

$n=1.533$

$W=\frac{0.123\times 2.076(140-20)}{1.533-1}$

$W=57.48 kJ$

From Energy balance

$E_{in}-E_{out}=\Delta E_{system}$

Neglecting kinetic and Potential Energy change

$Q_{in}+W_{in}=change\ in\ Internal\ Energy$

Change in Internal Energy $\Delta U=u_2-u_1$

$\Delta U=mc_v(T_2-T_1)$

$\Delta U=0.123\times 3.115(140-20)$

$\Delta U=45.977 kJ$

$Q_{in}+57.48=45.977$

$Q_{in}=-11.50 kJ$

i.e. Heat is being removed

3 0

3 years ago

A proton moving in the positive x direction with a speed of 9.9 105 m/s experiences zero magnetic force. When it moves in the po

Alex

Answer:

The magnitude of the magnetic field is 1.01T and its direction is in the negative x direction

Explanation:

In order to calculate the magnitude and direction of the magnetic field, you take into account the following equation for the magnetic force on the proton:

$\vec{F_B}=q\vec{v}\ X\ \vec{B}$ (1)

v: speed of the proton = 9.9*10^5 m/s

q: charge of the proton = 1.6*10^-19C

B: magnetic field = ?

FB: magnetic force on the proton = 1.6*10^-13N

When the proton travels in the positive y direction (^j), you have that the proton experiences a force in the positive z direction (+^k). To obtain this direction of the magnetic force on the proton, it is necessary that the magnetic field points in the negative x direction, in fact, you have:

^j X (-^i) = -(-^k)=^k

To obtain the magnitude of the magnetic field you use:

$F_B=qvBsin90\°=qvB\\\\B=\frac{F_B}{qv}=\frac{1.6*10^{-13}N}{(1.6*10^{-19}C)(9.9*10^5m/s)}\\\\B=1.01T$

The magnitude of the magnetic field is 1.01T and its direction is in the negative x direction

8 0

3 years ago

The force that acts on an object lying on a surface, acting in a direction perpendicular to the surface is called ____________

DanielleElmas [232]

If it is on land gravitational force
If it is on water thrust

8 0

2 years ago