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AlekseyPX
3 years ago
15

A high-speed bullet train accelerates and decelerates at the rate of 10 ft/s2. its maximum cruising speed is 120 mi/h. (round yo

ur answers to three decimal places.) (a) what is the maximum distance the train can travel if it accelerates from rest until it reaches its cruising speed and then runs at that speed for 15 minutes?
Physics
1 answer:
valina [46]3 years ago
3 0
What is the maximum distance the train can travel if it accelerates from rest until it reaches its cruising speed and then runs at that speed for 15 minutes?

d = vo*t + 0.5*a*(t**2)  ..........................(vo= initial speed = 0; a= acceleration; t=time, d = distance)

Vf  = vo  + a*t      (final speed, in this case it will be the cruising speed)


Since vo = 0 (starts from rest)

t = Vf/a

d = 0 + 0.5*a*((Vf/a)**2)

d =  (0.5/a)*(Vf)**2

a = 24545 miles/h2 = 10ft/s2


d1 =  (0.5/24545 miles/h2)*(120 mi/h)**2 = 0.293 miles

From cruising speed, distance traveled after 15 minutes (0.25h)

v = d/t ...................> d2 =v*t = <span>120 mi/h (0.25h)</span> = 30 miles

Maximum distance the train can travel,

D = d1 + d2 = 0.293 + 30  miles = 30.293 miles







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Answer:

1400 N

Explanation:

Verá, durante el salto mortal, el piloto se mueve en una trayectoria circular y la fuerza que actúa sobre él es una fuerza centrípeta.

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How much time does it take a dropped object to fall 180 m on Earth?
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Answer:

6s

Explanation:

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7 0
3 years ago
In a 49 s interval, 595 hailstones strike a glass window of an area of 0.954 m at an angle of 25° to the window surface. Each ha
eduard

Average  force on the window: 0.32 N

Explanation:

The average force exerted on the window is given by Newton's second law

F=\frac{\Delta p}{\Delta t}

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In order to find the change in momentum, we have to consider only the component of the hailstone's momentum perpendicular to the window, therefore:

p_i =m u sin \theta is the initial momentum of one hailstone, with

m = 7 g = 0.007 kg is the mass

u=4.5 m/s is the initial speed

\theta=25^{\circ} is the angle with the window

The final momentum is

p_f = mv sin \theta

where

v = 4.5 m/s is the final speed (the  collision is elastic so the speed is equal, while the direction changes)

\theta=-25^{\circ} (after the rebound, the direction has changed)

So the change in momentum of 1 hailstone is

\Delta p = mv sin(-25^{\circ})-mu sin(25^{\circ})=-2mu sin(25^{\circ})=-0.0266 kg m/s

We are interested only in the magnitude, so

\Delta p = 0.0266 kg m/s

There are 595 hailstones hitting the window in 49 s, so the total change in momentum is

\Delta p = 595\cdot 0.0266 = 15.8 kg m/s

And therefore, the average force on the window is

F=\frac{\Delta p}{\Delta t}=\frac{15.8}{49}=0.32 N

Learn more about  force:

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egoroff_w [7]

Answer:

Friction and air resistance cause some of his kinetic energy to be “lost”. This makes him slow down.

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The law of conservation of energy states that in absence of frictional forces, the mechanical energy of an object (given by the sum of its kinetic and potential energy) is conserved. In such a situation, the skateboarder would never stop his motion, because potential energy is continuously converted into kinetic energy and vice-versa, but the total energy remains the same so he would never stop.

In a real world, however, this is not true. In fact, in a real world some frictional force are present, in particular:

- friction: this force is due to the contact between the skateboard and the surface of the halfpipe, and its direction is always opposite to the motion of the skateboarder

- Air resistance: this force is due to the resistance opposed by the molecules of air that the skateboarder meets during his motion, and its direction is also opposite to the motion of the skateboarder

This two forces are said to be non-conservative forces, which means that they cause some of the mechanical energy of the skateboarder to be "lost", in the sense that it is dissipated as heat and it is no longer available for the skateboarder.

Therefore, the correct option is

Friction and air resistance cause some of his kinetic energy to be “lost”. This makes him slow down.

7 0
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