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3 years ago

A red train travelling at 72 km/h and a green train travelling at 144 km/h are headed toward each

Physics

1 answer:

abruzzese [7]3 years ago

6 0

Answer:

Collision will occur.

Speed of red train when they collide = 0 m/s.

Speed of green train when they collide = 10 m/s.

Explanation:

Speed of red train = 72 km/h = 20 m/s

Speed of green train = 144 km/h = 40 m/s.

Deceleration of trains = 1 m/s²

For red train:-

Equation of motion v = u + at

u = 20 m/s

v = 0 m/s

a = -1 m/s²

Substituting

0 = 20 - 1 x t

t = 20 s.

Equation of motion s = ut + 0.5at²

u = 20 m/s

t = 20 s

a = -1 m/s²

Substituting

s = 20 x 20 - 0.5 x 1 x 20² = 200 m

So red train travel 200 m before coming to stop.

For green train:-

Equation of motion v = u + at

u = 40 m/s

v = 0 m/s

a = -1 m/s²

Substituting

0 = 40 - 1 x t

t = 40 s.

Equation of motion s = ut + 0.5at²

u = 40 m/s

t = 40 s

a = -1 m/s²

Substituting

s = 40 x 40 - 0.5 x 1 x 40² = 800 m

So green train travel 800 m before coming to stop.

Total distance traveled = 800 + 200 = 1000 m>950 m.

So both trains collide.

Distance traveled by green train when red train stops(t=20s)

Equation of motion s = ut + 0.5at²

u = 40 m/s

t = 20 s

a = -1 m/s²

Substituting

s = 40 x 20 - 0.5 x 1 x 20² = 600 m

Total distance after 20 s = 600 + 200 = 800 m< 950m . So they collide after red train stops.

Speed of red train when they collide = 0 m/s.

Distance traveled by green train when they collide = 950 - 200 = 750 m

Equation of motion v² = u² + 2as

u = 40 m/s

s= 750 m

a = -1 m/s²

Substituting

v² = 40² - 2 x 1 x 750 = 100

v = 10 m/s

Speed of green train when they collide = 10 m/s.

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3 years ago

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3 years ago

A satellite orbiting Earth at an orbital radius r has a velocity v. Which represents the velocity

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Answer:

v / √5

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3 years ago

A nuclear power plant generates 3000 MW of heat energy from nuclear reactions in the reactor's core. This energy is used to boil

kondaur [170]

Answer:

a) $\eta_{th} = 46.1\,\%$ , b) $\eta_{th,real} = 36.667\,\%$

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$\eta_{th} = \left(1-\frac{T_{L}}{T_{H}} \right)\times 100\,\%$

Where:

$T_{L}$ - Temperature of the cold reservoir (Condenser), measured in K.

$T_{H}$ - Temperature of the hot reservoir (Evaporator), measured in K.

The maximum possible thermal efficiency is:

$\eta_{th} = \left(1-\frac{298.15\,K}{553.15\,K} \right)\times 100\,\%$

$\eta_{th} = 46.1\,\%$

b) The actual efficiency of the plant is the ratio of net power to input heat rate expressed in percentage:

$\eta_{th, real} = \frac{\dot W}{\dot Q_{in}} \times 100\,\%$

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3 years ago

please explain!! 15. You want to calculate the displacement of an object thrown over a bridge. Using -10 m/s2 for acceleration d

qwelly [4]

I will be making the assumption that you aren't actually really throwing the object over a bridge but rather dropping it as no initial velocity is actually given, which is required to do this problem. This will mean that initial velocity will be zero in this case.

First off, let's state all of the information we are given (the five kinematic quantities)

v₁ = 0 m/s

v₂ = cannot be determined

Δd = ?

Δt = 8 seconds

a (g) = 10 m/s² [down]

Now analyzing what we have, we can determine that we have 3 given quantities, 1 we must solve for, and 1 that cannot be found given our current information.

The five kinematic equations are useful because they all contain four kinematic quantities, and with different combinations too. In this case, we have three (v₁, Δt, a) and have to solve for Δd. The kinematic equation that fits with this would be:

Δd = v₁Δt + 0.5(a)(t)²

We can plug in our given values now.

Δd = 0 m/s(8 s) + 0.5(10 m/s²)(8 s)²

Δd = 0.5(10 m/s²)(8 s)²

Δd = <u>3</u>20 m

Therefore, the total displacement of the object would have to be 300m. (Due to significant digit rules)

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3 years ago