physics problem help!!

[JB513 10+ year member]

I feel retarded and i know i am already but for some reason i can not figure this one out. Can anyone help out? If you could explain how ya did it that would help even more seeing as i will have more of these to do in the future teacher just didnt explain it well.

A. Suzie (of mass 100 kg) is roller-blading down

the sidewalk going 20 miles per hour. She

notices a group of workers down the walkway

who have unexpectedly blocked her path, and

she makes a quick stop in 0.2 seconds.

What is Suzie’s average acceleration?

Answer in units of m/s^2.

B. What force was exerted to stop Suzie?

Answer in units of N.

Thanks if you can help if not well do what this forum does best. Thanks!

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[Mike465 10+ year member]

Ok well it has been a while for me but here we go.

Aav =delta v/delta t

So you have you speed of 20mps that you need to convert to meters per second

1 miles per hour = 0.44704 meters per second

20 miles per hour = 8.9408 meters per second

Now, we know what delta v is and we know what delat t is so

8.9408 meters per second/ 0.2 seconds = -44.704 meters per second squared was the average acceleration ( it is - because she is slowing down)

Now for part B

 

[Mike465 10+ year member]

force (f) = Mass(m) * acceleration (a)

So we know what here acceleration is so plug in the numbers

F=100kg * 44.704 m/s^2

F=4470.4N

 

[JB513 10+ year member]

Thats the way i tried it the first time i looked at it but I didnt think the answer seemed practical. When I put that in as the answer it said it was wrong anyone else know? I have 6 more chances lol.

 

[JB513 10+ year member]

I think i have to do something with the 100kg but im not sure.

 

[Mike465 10+ year member]

I believe that a newton is expressed as kg/(m/s^2) if not then convert the kg to what is is suposed to be. Sorry, it's been 3 years since I have taken physics

 

[JB513 10+ year member]

I completely understand man no worries.

 

[KHARPS 10+ year member]

I think it's 44.7N

V=at+V0

8.94m/s^2=a(0.2)+0

8.94/0.2=a

a=44.7N

 

[KHARPS 10+ year member]

That's my guess....I'm terrible at physics though so I'm probably wrong.

 

[Mike465 10+ year member]

I think it's 44.7N
V=at+V0

8.94m/s^2=a(0.2)+0

8.94/0.2=a

a=44.7N

Yes, but it is a negative acceleration but it is expressed in this case as m/s^2. Newton is an expression of force.

 

[GabeC 10+ year member]

12

 

[KHARPS 10+ year member]

Yes, but it is a negative acceleration but it is expressed in this case as m/s^2. Newton is an expression of force.

Yeah you're right. I accidently put N for some reason.

 

[Mike465 10+ year member]

I completely understand man no worries.

Look up how a newton is expressed.

 

[Mike465 10+ year member]

Yeah you're right. I accidently put N for some reason.

Happens to the best of us

 

[stillfly45 10+ year member]

r u doing webassign??