Physics Problem! Help

[somebody]

Here is the question, i try to think it over and ended up with nothing.

 

Consider an infant who weighs 100N. During the year she srows so that each dimansion of her body increases by 5%. How much will she then weigh?(assume her density remains the same)

 

 

and one more question: Student in a lab measure the speed of a steel ball launched horizontally from a table top to be 4.0 m/s. if the table top is 1.5 m above the floor, where should they place a 20-cm tall tin coffee can to catch the ball wen it lands?

 

i solve this problem and here it is:

h=1/2[gt^2]

t^2=1.5 s^2/5

t=.548 sec

 

x=vt

x=4.0m/s*0.548 s

x=2.192 which is how far you should have your ball fallen to but i cant figure out how to calculate the 20cm tall can and where to place it?

 

so please help me with both if you can ;)

[C1ay]

Here is the question, i try to think it over and ended up with nothing.

 

Consider an infant who weighs 100N. During the year she srows so that each dimansion of her body increases by 5%. How much will she then weigh?(assume her density remains the same)

That's not enough information. When you say every, does that mean for instance that the arm grows 5% longer or each arm segment and each finger all grow 5% longer? I'm inclined to think you're simply asking if a general 5% increase is a 5N growth.

Student in a lab measure the speed of a steel ball launched horizontally from a table top to be 4.0 m/s. if the table top is 1.5 m above the floor, where should they place a 20-cm tall tin coffee can to catch the ball wen it lands?

 

i solve this problem and here it is:

h=1/2[gt^2]

t^2=1.5 s^2/5

t=.548 sec

 

x=vt

x=4.0m/s*0.548 s

x=2.192 which is how far you should have your ball fallen to but i cant figure out how to calculate the 20cm tall can and where to place it?

 

so please help me with both if you can ;)

Imagine that the 1.5m height of the tabletop is simply reduced by the 20cm height of the can. What distance would the ball travel before it hit the floor?

[somebody]

hey that helps thanks, but not sure about the growth problem, i do not have further information. but i will ask my proffesor briefly though!

[somebody]

wait does that mean that i have to calculate the time again with 1.3 m Height and then get range?

[C1ay]

wait does that mean that i have to calculate the time again with 1.3 m Height and then get range?

yep

[UncleAl]

If you cannot understand bonehead physics, fail the course and release resources to people who can understand physics.

 

(100 N)(1.05)^3

(Assume a spherical homogeneous isotropic adiabatic cow...)

 

Resolving the components of a ballistic vector is trivial at this level. Do the obvious.

[somebody]

dude i though this was suppose to be a helpful forum, not a fun making. We all have our weaknesses and strengths. SO physics is not mine. So that is y i expect you guys to help me out to understand physics better! ;)

[C1ay]

UncleAl can be rather curt with his opinion sometimes. I'm sure you will find most here to be helpful and friendly. By the way, Welcome to Hypography.

[Aki]

Somebody: don't worry. You're doing fine. You are wanting to learn and eager to ask your question, and everyone should admire that. If you have any more questions, don't be scared to ask. Many people here are friendly, and they'll answer your question.

[Qfwfq]

Welcome to Hypo, Somebody!

 

Ask questions, and if occasionally someone like UA gives you that kind of reply... ignore, ignore, ignore. ;)

 

Oh, yes. I also would have taken it that the volume increase is the cube of 1.05 (1,157625) as I interpret "5% in each dimension" as being a 3-D scale increase. Uniform density then means the mass will also increase by the same factor. ;)

[somebody]

Thanks guys, i am taking summer course and it is going pretty fast so needed outside help as well so i am here.....

 

Oh, yes. I also would have taken it that the volume increase is the cube of 1.05 (1,157625) as I interpret "5% in each dimension" as being a 3-D scale increase. Uniform density then means the mass will also increase by the same factor. :hihi:

 

 

you mean 105 cube not 1.05 so as the baby grows 5% in each dimension and we are considering its a 3 dimention. So the total baby weight would be 1157625? and if it is then isnt it too much?

[CraigD]

you mean 105 cube not 1.05 so as the baby grows 5% in each dimension

No. “Grows by 5% in each dimension” means “Has 105% of his original height, 105% of his original width, 105% of his original depth”. “Percent” literally means “divided by 100”, so 105% = 105/100 = 1.05

 

You might find it helpful to imagine that your baby is cube shaped, with height, width, and depth each 1 meter. Since volume of a cube is height * width * depth, his original volume was 1 * 1 * 1 = 1 m^3 (one meter cubed, or one cubic meter). His new volume is 1.05 * 1.05 * 1.05 = 1.157625. Since his density and the acceleration of gravity is unchanged, his new weight, then, is 115.7625 n

 

Notice that this is the same result you get if you imagine the baby is a sphere with radius 1 m. In that case, his original volume is 4 * Pi * 1^3 / 3, his new volume 4 * Pi * 1.05^3 / 3. Notice that the 4*Pi/3 part of both expressions is constant, so you can say the his new volume is 1.05^3, which is the same as 1.05*1.05*1.05 and 1.157625.

 

Above all else, always check your arithmetic against common sense. You know there’s no way a roughly 10 kg baby could grow by 5% and gain more than 100 metric tons!

 

Now, so we all know you’re not just using us to do you homework, answer these 3 questions:

“what would the baby weigh if it grew another 10% in each dimension?”

and

“what would a 10 KG baby mass if it grew 25% in height, and 10% in girth?”

and

“A bullet is fired with a muzzle velocity of 850 m/s, on level ground, from a height of 1.7 meters, on the surface of the moon, where the acceleration of gravity is 1.6 m/s^2. How far does it travel before striking the surface.”

[somebody]

 

Oh, yes. I also would have taken it that the volume increase is the cube of 1.05 (1,157625) as I interpret "5% in each dimension" as being a 3-D scale increase. Uniform density then means the mass will also increase by the same factor. :hihi:

 

Thanks guys, i apreciate your help, but isnt 1157625 N^3 kinda too much?

[somebody]

forget it what i said in previous post "accident", and i am sorry if i am using you to do my homework but i am having serious problems with science classes becuase of my language :sad:

 

Q-1. What would the baby weight if it grew another 10% in each dimension?

Ans- it would be 115% of h,w,l so 1.15*1.15*1.15 =1.520875 m^3 . So the baby would wiegh 152.0875 N.

 

Q-3. A bullet is fired with a muzzle velocity of 850 m/s, on level ground, from a height of 1.7 meters, on the surface of the moon, where the acceleration of gravity is 1.6 m/s^2. How far does it travel before striking the surface?

Ans- Hum.. i havent done much of the projectile problems so not sure but here is what i think...

d=1/2gt^2 1.7m=1/2*1.6m/s^2*t^2 t=1.46sec

 

d=v*t d=850 m/s * 1.46s d=1241 m

 

the the bullet would travel 1241m and i think i am wrong!

 

dont have time for the 2nd question gtg,

but i will be solving it before the day ends :hihi:

[UncleAl]

Ask questions, and if occasionally someone like UA gives you that kind of reply... ignore, ignore, ignore.

Nobody cares what the answers are. The questions are answered every term. They are trivial in content. Homework and tests exist to create understanding and demonstrate objective competence.

 

If he sat in lecture and read his textbook and still cannot successfully handle problems such as these, something is seriously deficient at the front end and/or at the back end. Autodidact There is no excuse for being unable to perform at this level - for whatever reason. Make a choice while there are still good choices to be voluntarily made:

 

1) Save the drama for your mama, maggot. Get down and push. You must understand the material to perform. Memorizing formulae without understanding won't get you anywhere useful. The answer to new weight vs. increasing dimensions by 5% is particularly telling - off by a six orders of magnitude. Anybody who would post such an answer, a 1 in 20 increase giving a millionfold change, hasn't a clue. Too many signficant figures, too.

 

2) Get out. Pursue something you can do.

 

3) Implode. You are a VICTIM! That is always the easy route. Evolution is a hoot - but only if you are a survivor.

 

30% of the population is purely incapable of finishing high school. It has been that way, with excellent documentation, since at least the 1850s. In Europe this 30% is shunted to manual arts and trades to uncover other real world abilities and render them into productive citizens. Many of them are thereby saved. In the US they are all discarded, then perpetually subsidized with Welfare or imprisonment. Stupid.

 

Who finished second to Roger Bannister? Name one ruler Alexander the Great defeated while conquering the entire known world. Who ran against current US President Bush the Lesser in the 2000 election?

 

http://www.mazepath.com/uncleal/mayberry.jpg

hint

 

Make the choice. Succeed, change, or die. Be certain at least one person cares about the outcome: you.

[somebody]

ok for the second problem, 125% of height, 110% in growth and the weidth doesnt grow so its 100%.

 

1.25 * 1.10 * 1.00 = 1.375 so 1.375 * 10kg = 13.75 kg

 

and once again i apologize if i have been taking advantage of this forum, i didnot mean any harm. For these 3 problems i have good chances of getting them wrong. I do not like Physics but like chemistry. So dont get mad if i didnt learn anything from your example,

 

Craidg tell you the truth you have explained this problem better then my proffessor explains small problems like velocity and acceleration. :hihi: Just between you and me :sad: its pretty cool that you give me some problems to work with after my question, i kinda enjoy it and it gives me good practice!

[somebody]

Look uncle i do not like physics but its a requirement, no offence to physicians or physics lover, everyone is different so if you expect everybody to understand physics like this BASIC one then you are wrong.

 

tell me last time you see some artist use much of an acceleration? I am not saying it's worthless but most people know common physics that they need to know!