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My name is Ann [436]
3 years ago
13

Please help me with this question guys.

Physics
1 answer:
katen-ka-za [31]3 years ago
7 0

Answer:

<em>The average speed is 22.2 km/h</em>

Explanation:

<u>Average Speed</u>

Given an object travels a total distance d and took a total time t, then the average speed is:

\displaystyle \bar v=\frac{d}{t}

The mailman first drives d1=7 km at v1=15 km/h. The time taken to drive is:

\displaystyle t1=\frac{d1}{v1}=\frac{7}{15}=0.467\ h

Then he drives d2=7 km at v2=43 km/h taking a time of:

\displaystyle t2=\frac{d2}{v2}=\frac{7}{43}=0.163\ h

The total time is

t=0.467 h + 0.163 h = 0.63 h

The total distance is

d = 7 km + 7 km = 14 km

The average speed is:

\displaystyle \bar v=\frac{14}{0.63}=22.2\ km/h

The average speed is 22.2 km/h

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A student does 1,000 J of work when she moves to her dormitory. Her internal energy is decreased by 3,000 J. Determine the heat
Alenkinab [10]

Answer:

-2000 J (heat lost)

Explanation:

We can solve the problem by using the 1st law of thermodynamics:

\Delta U = Q-W

where

\Delta U is the change in internal energy of a system

Q is the heat absorbed by the system

W is the work done by the system

In this situation, we have

W=1000 W (work done by the student)

\Delta U = -3000 J (decrease in internal energy)

So the heat is

Q=\Delta U + W = -3000 J +1000 J = -2000 J

And the negative sign means the student has lost heat.

3 0
4 years ago
Give two examples of direct current electricity.​
ludmilkaskok [199]

Answer:

<h3>Ion beams and Electrochemical are two examples of direct current electricity.</h3>
6 0
4 years ago
Using the Bohr model, what is the ratio of the energy of the nth orbit of a triply ionized beryllium atom (Be3+, Z = 4) to the e
emmainna [20.7K]

Answer:

16

Explanation:

solution:

by taking the ratio of the energy E_n,be of the nth orbit of a beryllium atom

Z_be=4 to the energy E_n,h of the nth orbit of a hydrogen (Z_h=1) atom  gives

E_n,B/E_n,H=-(2.18*10^-18)*Z^2_BE/-(2.18*10^-18)*Zh^2/n^2

                    =Z^2_BE+/Z^2_H

                    =(4)^2/(1)^2

                    = 16

8 0
4 years ago
Does a car accelerate when it goes around a corner at a constant speed?
Evgen [1.6K]
Yes, it does. Acceleration is defined as the rate of change of velocity. Velocity is the rate of change of position with a given direction i.e. speed with direction.So even though the speed of the turning car is constant the velocity is not. This means that the velocity is changing, and the rate of change of velocity is called acceleration. Hence, the car is accelerating.
6 0
4 years ago
Hydrogen sulfide, H2S, and hydrogen chloride, HCl, are both gases at temperatures above –50 °C.
vladimir1956 [14]

Explanation:

A gas at higher temperature is able to gain more heat from the environment/surroundings and has more kinetic energy to diffuse at a faster rate.

Hence a temperature at -20°C is more ideal.

Molar mass of H2S = 34.07g/mol

Molar mass of HCl = 36.45g/mol

Since H2S has a smaller molar mass, the same number of moles of H2S gas will diffuse faster as compared to the same number of moles of HCl gas.

Hence the answer is Hydrogen sulfide at -20°C. (D)

5 0
3 years ago
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