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3 years ago

9

Using F=ma, explain why a train is more difficult to start moving and more difficult to bring to a stop than an average sized ca

r.

1 answer:

seropon [69]3 years ago

6 0

Answer:

M_Train>> m_car a_train <a_car

Explanation:

To start the movement of the train or the car, the motorcycle applies a force on the wheels, which starts the acceleration in the case of the train, it has a much greater mass than that of the car, for which to obtain the same acceleration necessary a much greater force

a = F / m

as the mass of the train is greater than that of the car.

a_train <a_car

Something similar happens when the vehicles stop, the engine stops applying force forward and the brakes apply a force backward that creates a negative acceleration that slows down, again as the mass of the train is much greater than the of the car its negative acceleration is much less.

It is good to clarify that to compensate for this the trains have a braking system on all wheels

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A yet-to-be-built spacecraft starts from Earth moving at constant speed to the yet-tobe-discovered planet Retah, which is 20 lig

Gre4nikov [31]

Answer:

The time elapsed at the spacecraft’s frame is less that the time elapsed at earth's frame

Explanation:

From the question we are told that

The distance between earth and Retah is $d = 20 \ light \ hours = 20 * 3600 * c = 72000c \ m$

Here c is the peed of light with value $c = 3.0*10^8 m/s$

The time taken to reach Retah from earth is $t = 25 \ hours = 25 * 3600 =90000 \ sec$

The velocity of the spacecraft is mathematically evaluated as

$v_s = \frac{d }{t}$

substituting values

$v_s = \frac{72000 * 3.0*10^{8} }{90000}$

$v_s = 2.40*10^{8} \ m/s$

The time elapsed in the spacecraft’s frame is mathematically evaluated as

$T = t * \sqrt{ 1 - \frac{v^2}{c^2} }$

substituting value

$T = 90000 * \sqrt{ 1 - \frac{[2.4*10^{8}]^2}{[3.0*10^{8}]^2} }$

$T = 54000 \ s$

=> $T = 15 \ hours$

So The time elapsed at the spacecraft’s frame is less that the time elapsed at earth's frame

7 0

3 years ago

What distance does the car cover in the first 4.0 seconds of its motion?

CaHeK987 [17]

The distance covered is (4) times (the car's average speed during that time).

6 0

3 years ago

What is/are the external cause code(s) for a passenger involved in a mva that lost control on the highway and hits a guardrail?

Sholpan [36]

Here is the answer. The external cause code for a passenger that is involved in a MVA that lost control on the highway and hits a guardrail is E815. Your fifth digit is a 1 for a motor vehicle passenger. You would use an additional E code when a place of occurrence (example, home or parking lot) is documented. In this case, the location is documented as the highway. Hope this helps.

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4 years ago

A wall has inner and outer surface temperatures of 25◦C and 8◦C, respectively. The interior and exterior air temperatures are 35

Angelina_Jolie [31]

Answer:

a) $\frac{\dot Q}{A} =60\ W.m^{-2}$

b) $\frac{\dot Q}{A} =110\ W.m^{-2}$

c) The wall may not be under steady because the two surfaces of the wall are exposed to the air at different temperatures and they have different convective coefficient.

Explanation:

Given:

temperature of the inner surface of the wall, $T_i=25^{\circ}C$

temperature of the outer surface of the wall, $T_o=8^{\circ}C$

temperature of the air outside, $T_{ao}=-3^{\circ}C$

temperature of the air inside, $T_{ai}=35^{\circ}C$

coefficient of heat convection on outside, $h_o=10\ W.m^{-2}.K^{-1}$

coefficient of heat convection on inside, $h_i=6\ W.m^{-2}.K^{-1}$

a)

The heat flux between the interior air and the wall:

The convective heat transfer rate is given as,

$Q=h_i.A.\Delta T$

$\Rightarrow \frac{\dot Q}{A} =h_i\times (T_{ai}-T_i)$

$\frac{\dot Q}{A} =6\times (35-25)$

$\frac{\dot Q}{A} =60\ W.m^{-2}$

b)

The heat flux between the exterior air and the wall:

$\Rightarrow \frac{\dot Q}{A} =h_o\times (T_{ao}-T_i)$

$\frac{\dot Q}{A}=10\times (8-(-3))$

$\frac{\dot Q}{A} =110\ W.m^{-2}$

c)

The wall may not be under steady because the two surfaces of the wall are exposed to the air at different temperatures and they have different convective coefficient.

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4 years ago

Sea and land breezes are caused because ____.

Bogdan [553]

Sea and land breezes are caused because the land heats and cools more quickly than the water. The correct option for the given question is option “b”. A sea breeze is a breeze that blows from the sea to the land. The land becomes coo quicker than the sea resulting in the sea breeze. A land breeze is caused during the day when the land is hotter than the sea. The hot air blows from the land towards the sea.

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3 years ago

Read 2 more answers