Hovercraft B/C

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Birdmusic
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Hovercraft B/C

Post by Birdmusic »

No hovercraft question marathon yet? I think I'll start one.

A train has an initial velocity of 4 m/s. It speeds up with constant acceleration to 8 m/s over a period of 2 seconds. What is its displacement? What equation did you use?
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heyimben
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Re: Hovercraft B/C

Post by heyimben »

24m? I literally just found a basic formula for displacement...
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Re: Hovercraft B/C

Post by Zioly »

I used delta(x)=v(initial)t+1/2at^2, one of the kinematic equations.

I also got 24 meters.
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Re: Hovercraft B/C

Post by Froggie »

Make sure to use the “HIDE” thing next time. ;)
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Re: Hovercraft B/C

Post by Birdmusic »

heyimben wrote:24m? I literally just found a basic formula for displacement...
Correct! Since you answered first, you get to post the next question!
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Re: Hovercraft B/C

Post by heyimben »

Birdmusic wrote:
heyimben wrote:24m? I literally just found a basic formula for displacement...
Correct! Since you answered first, you get to post the next question!
If a person were walking at the average speed of 2.5 mph from District 12 to District 13 and it takes a week to get there, how fast is the hovercraft traveling from District 12 to District 13, which makes it there in 45 min?
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Re: Hovercraft B/C

Post by WhatScience? »

heyimben wrote:
Birdmusic wrote:
heyimben wrote:24m? I literally just found a basic formula for displacement...
Correct! Since you answered first, you get to post the next question!
If a person were walking at the average speed of 2.5 mph from District 12 to District 13 and it takes a week to get there, how fast is the hovercraft traveling from District 12 to District 13, which makes it there in 45 min?
heyimben....how much of that time is gone to sleep?
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Re: Hovercraft B/C

Post by Justin72835 »

heyimben wrote:
Birdmusic wrote:
heyimben wrote:24m? I literally just found a basic formula for displacement...
Correct! Since you answered first, you get to post the next question!
If a person were walking at the average speed of 2.5 mph from District 12 to District 13 and it takes a week to get there, how fast is the hovercraft traveling from District 12 to District 13, which makes it there in 45 min?
You can assume that the person is walking nonstop (without taking rest) because he uses the term "average speed".

One week is equivalent to 168 hours. If the person walks at a speed of 2.5 mph for 168 hours, then the distance between the two points is 420 miles. To find the average speed of the hovercraft, use the formula distance/time, or in this case 420 miles/0.75 hours = 560 mph.

Next question: You have a solid cube of mass 'm' which is attached to a nearby wall using a massless, ideal spring of constant 'k'. If you launch an arrow of velocity 'v' and mass 'M' directly at the solid cube, what is the maximum compression of the spring if:

1) the arrow sticks into the solid after hitting it?

2) the arrow bounces off of the cube perfectly elastically?
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Re: Hovercraft B/C

Post by SciolyMaster »

heyimben wrote:24m? I literally just found a basic formula for displacement...
That is incorrect. 8 m/s^2 is what the train accelerates TO from the initial velocity of 4 m/s^2, not the acceleration itself, which would be (8-4)/2 = 2. Therefore, d = vi*t + 0.5*a*t^2 = 4*2 + 0.5*2*2^2 = 12, so the correct answer is 12 meters.
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Re: Hovercraft B/C

Post by UTF-8 U+6211 U+662F »

Justin72835 wrote:Next question: You have a solid cube of mass 'm' which is attached to a nearby wall using a massless, ideal spring of constant 'k'. If you launch an arrow of velocity 'v' and mass 'M' directly at the solid cube, what is the maximum compression of the spring if:

1) the arrow sticks into the solid after hitting it?

2) the arrow bounces off of the cube perfectly elastically?
1) kMv/(M+m) 2) 2kMv/(M+m)
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