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Alekssandra [29.7K]
3 years ago
12

How much work must be done by frictional forces in slowing a 1000-kg car from 26.1 m/s to rest? a.3.41 x 10^5 J b.2.73 x 10^5 J

c.4.09 x 10^5 J d.4.77 x 10^5 J
Physics
1 answer:
algol133 years ago
6 0

Answer:

Work done by the frictional force is 3.41\times 10^5\ J

Explanation:

It is given that,

Mass of the car, m = 1000 kg

Initial velocity of car, u = 26.1 m/s

Finally, it comes to rest, v = 0

We have to find the work done by the frictional forces. Work done is equal to the change in kinetic energy as per work - energy theorem i.e.

W=k_f-k_i

W=\dfrac{1}{2}m(v^2-u^2)

W=\dfrac{1}{2}\times 1000\ kg(0^2-(26.1\ m/s)^2)

W = −340605 J

or

W=3.41\times 10^5\ J

Hence, the correct option is (a).

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Write down the (real) electric and magnetic fields for a monochromatic plane wave of amplitude E0 , frequency w, and phase angle
jeka57 [31]

Answer:

a) the oscillation of this field is in phase, when the magnetic field goes in the negative direction of y, the elective field goes in the positive direction of the z axis

b) the direction of the magnetic field perpendicular to this electric field and the speed in the negative x the magnetic field goes in the x direction and in the direction (1, - 1.1)

Explanation:

a) the polarization the determined wave oscillates the electric field, which is the z axis

 As the wave travels on the negative x-axis and the magnetic field is perpendicular, this field goes on the positive y-axis

the oscillation of this field is in phase, when the magnetic field goes in the negative direction of y, the elective field goes in the positive direction of the z axis

be) in the case of a polarization in the xi plane the magnetic field must go in the direction of the magnetic field perpendicular to this electric field and the speed in the negative x the magnetic field goes in the x direction and in the direction (1, - 1.1)

3 0
3 years ago
Harrison wanted to find out what soil works best for growing roses. He grew them in potting soil, clay, sand, and soil he found
zepelin [54]

Answer:

This question is asking to identify the following variables:

Independent variable (IV): TYPE OF SOIL

Dependent variable (DV): HEIGHT AND NUMBER OF LEAVES

Control group: None in this experiment

Constant: SAME ROSE PLANT, SAME TIME INTERVAL (1 WEEK)

Explanation:

Independent variable in an experiment is the variable that is manipulated or changed by the experimenter in order to effect a measurable outcome. In this case, the independent variable is the TYPE OF SOIL used.

Dependent variable is the measurable variable that responds to changes made to the independent variable. In this experiment, the dependent variable is the HEIGHT AND NUMBER OF LEAVES of each rose.

Constants or control variable is the variable that is kept unchanged or constant for all groups throughout the experiment. In this experiment, the constants are SAME ROSE PLANT, SAME TIME INTERVAL (1 WEEK).

Control group are the groups that does not receive the experimental treatment. In this case, all the groups received the experimental treatment (different soil types). Hence, there is no control

4 0
3 years ago
In a 400-m relay race the anchorman (the person who runs the last 100 m) for team A can run 100 m in 9.8 s. His rival, the ancho
melisa1 [442]

Answer:

largest lead = 3 m

Explanation:

Basically, this problem is about what is the largest possible distance anchorman for team B can have over the anchorman for team A when the final leg started that anchorman for team A won the race. This show that anchorman for team A must have higher velocity than anchorman for team B to won the race as at the starting of final leg team B runner leads the team A runner.

So, first we need to calculate the velocities of both the anchorman  

given data:

Distance = d = 100 m

Time arrival for A = 9.8 s

Time arrival for B = 10.1 s

Velocity of anchorman A = D / Time arrival for A

=100/ 9.8 = 10.2 m/s

Velocity of anchorman B = D / Time arrival for B

=100/10.1 = 9.9 m/s

As speed of anchorman A is greater than anchorman B. So, anchorman A complete the race first than anchorman B. So, anchorman B covered lower distance than anchorman A. So to calculate the covered distance during time 9.8 s for B runner, we use

d = vt

= 9.9 x 9.8 = 97 m  

So, during the same time interval, anchorman A covered 100 m distance which is greater than anchorman B distance which is 97 m.

largest lead = 100 - 97 = 3 m

So if his lead no more than 3 m anchorman A win the race.

5 0
3 years ago
Temperature and pressure of a region upstream of a shockwave are 295 K and 1.01* 109 N/m². Just downstream the shockwave, the te
seraphim [82]

Answer:

change in internal energy 3.62*10^5 J kg^{-1}

change in enthalapy  5.07*10^5 J kg^{-1}

change in entropy 382.79 J kg^{-1} K^{-1}

Explanation:

adiabatic constant \gamma =1.4

specific heat is given as =\frac{\gamma R}{\gamma -1}

gas constant =287 J⋅kg−1⋅K−1

Cp = \frac{1.4*287}{1.4-1} = 1004.5 Jkg^{-1} k^{-1}

specific heat at constant volume

Cv = \frac{R}{\gamma -1} = \frac{287}{1.4-1} = 717.5 Jkg^{-1} k^{-1}

change in internal energy = Cv(T_2 -T_1)

                            \Delta U = 717.5 (800-295)  = 3.62*10^5 J kg^{-1}

change in enthalapy \Delta H = Cp(T_2 -T_1)

                                 \Delta H = 1004.5*(800-295) = 5.07*10^5 J kg^{-1}

change in entropy

\Delta S =Cp ln(\frac{T_2}{T_1}) -R*ln(\frac{P_2}{P_1})

\Delta S =1004.5 ln(\frac{800}{295}) -287*ln(\frac{8.74*10^5}{1.01*10^5})

\Delta S = 382.79 J kg^{-1} K^{-1}

7 0
3 years ago
A scientist designs an experiment in which a light source is pointed at a substance and a light detector is placed on the opposi
Lostsunrise [7]
The answer is D. Either absorbed or reflected. The reason is because if no light is being shown on the other side, the substance is not letting any light pass through. Since we do not know anything else about the substance, we do not know which one of the two it is doing. The scientist would not see any light on the detector if 100% of the light is reflected and the same thing would happen if 100% of the light was absorbed.
5 0
3 years ago
Read 2 more answers
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