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gregori [183]
3 years ago
10

A car traveled 60km in 45 min.What is the cars average speed in km/hr

Physics
1 answer:
sergey [27]3 years ago
5 0

Given that,

Distance = 60 km

Time = 45 min

To find,

The average speed of the car.

Solution,

Average speed of an object is equal to the total distance divided by total time taken.

45 min = 0.75 hour

It can be given as :

V=\dfrac{60\ km}{0.75\ h}\\\\=80\ km/h

Therefore, the average speed of the car is 80 km/hr.

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At some instant and location, the electric field associated with an electromagnetic wave in vacuum has the strength 71.9 V/m. Fi
kirza4 [7]

Answer:

a) Magnetic field strength, B = 2.397 * 10⁻⁷ T

b) Total energy density, U = 4.58 * 10⁻⁸ J/m³

c) Power flow per unit area, S = 13.71 W/m²

Explanation:

a) Electric field strength, E = 71.9 V/m

The relationship between the Electric field strength and the magnetic field strength in vacuum is:

E = Bc where c = 3.0 * 10⁸ m/s

71.9 = B * 3.0 * 10⁸

B = 71.9 / (3.0 * 10⁸)

B = 23.97 * 10⁻⁸

B = 2.397 * 10⁻⁷ T

b) Total Energy Density:

U = \frac{1}{2} \epsilon_0E^2 +  \frac{1}{2} \frac{B^2}{\mu_0} \\U = \frac{1}{2}* 8.85 * 10^{-12}*71.9^2 +  \frac{1}{2} \frac{(2.397*10^{-7})^2}{4\pi*10^{-7}}\\U = 2.29 * 10^{-8} + 2.29 * 10^{-8}\\U = 4.58 * 10^{-8} J/m^3

c)Power flow per unit area

S = \frac{1}{\mu_0} EB\\S = \frac{1}{4\pi * 10^{-7} } * 71.9 * 2.397 * 10^{-7}\\S = 13.71 W/m^2

6 0
3 years ago
You find it takes 200 J of heat to take 4 kg of an unknown substance from 200 K to 240 K. It does not change phases during this
klasskru [66]

Answer:

300 K

Explanation:

First, we have find the specific heat capacity of the unknown substance.

The heat gained by the substance is given by the formula:

H = m*c*(T2 - T1)

Where m = mass of the substance

c = specific heat capacity

T2 = final temperature

T1 = initial temperature

From the question:

H = 200J

m = 4 kg

T1 = 200K

T2 = 240 K

Therefore:

200 = 4 * c * (240 - 200)

200 = 4 * c * 40

200 = 160 * c

c = 200/160

c = 1.25 J/kgK

The heat capacity of the substance is 1.25 J/kgK.

If 300 J of heat is added, the new heat becomes 500 J.

Hence, we need to find the final temperature, T2, when heat is 500 J.

Using the same formula:

500 = 4 * 1.25 * (T2 - 200)

500 = 5 * (T2 - 200)

100 = T2 - 200

=> T2 = 100 + 200 = 300 K

The new final temperature of the unknown substance is 300K.

7 0
3 years ago
A small 22 kilogram canoe is floating downriver at a speed of 5 m/s. What's the canoes kinetic energy? _______ Joules
netineya [11]
The non-relativistic formula for kinetic energy for low speeds is :

K.E = 0.5mv^2 = 0.5 * 22 * (5)^2 = 275 J
8 0
3 years ago
Read 2 more answers
Different structural forms of the same element are called
julia-pushkina [17]

Answer:

allotropes

Explanation:

4 0
3 years ago
Which of Newton's laws explains why satellites need very little fuel to stay in oribit?
Angelina_Jolie [31]

Sattelites don't need any fuel to stay in orbit. The applicable law is...."objects in motion tend to stay in motion". Having reached orbital velocity, any such object is essentially "falling" around the earth. Since there is no (or at least very little) friction in the vacuum of space, the object does not slow.... It simply continues.


Sattelites in "low" earth orbit do encounter some friction from the very thin upper atmosphere, and they will eventually "decay".

:)

4 0
3 years ago
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