Dynamics problems(force and friction and such)

[thelegend123]

3 problems

1. A 2.0 kg object is traveling at a constant speed of 1.4m/s[N] when it hits and ice patch. over the first 0.40m of the ice patch the object slows down to 0.85m/s[N]. what is coefficient of friction of the ice? (starting on a frictionless surface then slowing down)


2. an object starts from rest and then travels 6.0m

in 4.0s. if the coefficient of friction is 0.10 and there was an applied force of 9.0N

, what was the mass of the object?


3. Mr.Yahoo is pulling her friend's kids in a wagon with a force of 150N [E30*up] (which is equivalent to 130 N [E] and 75 N [up}. if the kids weigh 12kg, 8.0kg and the wagon weighs 3.0kg and the coefficient of friction is 0.43, what is their acceleration?


Thank you in advance, please try to show full work and calculations and an idea of what a freebody diagram looks like.​

 

[tiny-tim]

welcome to pf!

hi thelegend123! welcome to pf

show us what you've tried, and where you're stuck, and then we'll know how to help!

(start with 1.)

 

[thelegend123]

hi thelegend123! welcome to pf

show us what you've tried, and where you're stuck, and then we'll know how to help!

(start with 1.)

i stated all of my variables

i found the Fg = 19.6N and Fn = 19.6N i don't know where to go from here

 

[tiny-tim]

do the geometry first, then the physics

the geometry is to find the acceleration from the data

then use physics to find the force, and then the coefficient of friction

what do you get?
​

 

[thelegend123]

do the geometry first, then the physics

the geometry is to find the acceleration from the data

then use physics to find the force, and then the coefficient of friction

what do you get?
​

not tosure on how to find accel?

would it be using a kinematic equation v2^2 = v1^2 + 2ad

but i don't think D has direction

 

[tiny-tim]

would it be using a kinematic equation v2^2 = v1^2 + 2ad

that's right

but i don't think D has direction

i don't understand

(anyway, now I'm off to bed :zzz:)

 

[thelegend123]

do the geometry first, then the physics

the geometry is to find the acceleration from the data

then use physics to find the force, and then the coefficient of friction

what do you get?
​

i got acceleration is -1.5ish and Fnet is 3.1N

what now?

 

[tal444]

Good. Your Fnet is equal to your friction force, right? What is your formula for finding the force of friction?