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3 years ago

Alex swims at an average speed of 45 m/min.how far does he swim in 1min 24 sec?

Physics

1 answer:

Drupady [299]3 years ago

8 0

Answer: 72m/1 min and 24 secs

Explanation:

He swims .75m/sec. im pretty sure i got it but let me know and ill help you out if its wrong

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The Earth rotates once every day. What is the velocity of a person on its surface, if the radius of Earth is 6 million meters

LekaFEV [45]

Answer:

v = ω R

number of seconds in 24 hrs = 24 * 3600 = 86400 s / da = T (period)

f = 1 / T

ω = 2 Π f = 2 Π / T = 2 Π / 86400

v = 2 Π / 8.64E4 * 6.0E6 = 436 m / s

Check:

S = 2 Π * 6.0E6 = 3.77E7 m/da

S / T = 3.77E7 m/da / 8.64E4 s/da = 436 m / s

3 0

2 years ago

A closed, rigid tank fitted with a paddle wheel contains 2 kg of air, initially at 300 K. During an interval of 5 minutes, the p

anzhelika [568]

Answer:

The final temperature of the air is $T_2= 605 K$

Explanation:

We can start by doing an energy balance for the closed system

$\Delta KE+\Delta PE+ \Delta U = Q - W$

where

$\Delta KE$ = the change in kinetic energy.

$\Delta PE$ = the change in potential energy.

$\Delta U$ = the total internal energy change in a system.

Q = the heat transferred to the system.

W = the work done by the system.

We know that there are no changes in kinetic or potential energy, so $\Delta KE = 0$ and $\Delta PE=0$

and our energy balance equation is $\Delta U = Q - W$

We also know that the paddle-wheel transfers energy to the air at a rate of 1 kW and the system receives energy by heat transfer at a rate of 0.5 kW, for 5 minutes.

We use this information to calculate the total internal energy change $\Delta U=W+Q$ using the energy balance equation.

We convert the interval of time to seconds $t = 5 \:min = 300\:s$

$\Delta \dot{U}=\dot{W}+ \dot{Q}\\=\Delta U=(W+ Q)\cdot t$

$\Delta U=(1 \:kW+0.5\:kW)\cdot 300\:s\\\Delta U=450 \:kJ$

We can use the change in specific internal energy $\Delta U = m(u_2-u_1)$ to find the final temperature of the air.

We are given that $T_1=300 \:K$ and the air can be describe by ideal gas model, so we can use the ideal gas tables for air to determine the initial specific internal energy $u_1$

$u_1=214.07\:\frac{kJ}{kg}$

Next, we will calculate the final specific internal energy $u_2$

$\Delta U = m(u_2-u_1)\\\frac{\Delta U}{m} =u_2-u_1$

$\frac{\Delta U}{m} =u_2-u_1\\u_2=u_1+\frac{\Delta U}{m}$

$u_2=214.07 \:\frac{kJ}{kg} +\frac{450 \:kJ}{2 \:kg}\\u_2= 439.07 \:\frac{kJ}{kg}$

With the value $u_2=439.07 \:\frac{kJ}{kg}$ and the ideal gas tables for air we make a regression between the values $u = 434.78 \:\frac{kJ}{kg},T=600 \:K$ and $u = 442.42 \:\frac{kJ}{kg}, T=610 \:K$ and we find that the final temperature $T_2$ is 605 K.

3 0

3 years ago

A boy pushes a 50 kg wheelbarrow with a velocity of 0.5 m/s. If he uses a force of 10 N, how far does he push

labwork [276]

Answer:

d=1.25 m

Explanation:

fd=.5mv2-.5mv1; 10(d)=.5(50)(.5)-0; 10(d)=12.5; d=12.5/10; d=1.25 m

4 0

3 years ago

What property is primarily responsible for determining the type of electromagnetic energy and peak wavelength emitted by a star

Galina-37 [17]

Answer:B. Temperature

Explanation:The temperature of the star such as Sun is measured. Using this measurement, its peak wavelength and energy can be determined.For determination of wavelength, Wien's displacement law is used. This law states that, the sun like body emits all kinds of wavelengths and thus is nearly a black body.For black body, the peak wavelength emitted is inversely proportional to the temperature of the body. From the wavelength, energy can be calculated.Temperature is the property which is primarily responsible for determining the type of electromagnetic energy and peak wavelength emitted by star.

5 0

3 years ago

A spring has a 12 cm length. When a 200-g mass is hung from the spring, it extends to 27 cm. The hanging mass were pulled downwa

BartSMP [9]

Answer:

The equation of the time-dependent function of the position is $x(t)=5\cos(8.08t)$