# Homework Help: Frictional force problem

1. Jul 25, 2012

### inzektor95

1. The problem statement, all variables and given/known data

a toy is dragged along a rough floor by a child

(a) when the child applies a force of 0.50N horizontally the velocity is contant at 1.0 m/s. What is the force of friction on the toy?

(b)when the child pulls harder so that the applied force is 1.00N the velocity of the toy increases uniformly to 2.0 m/s in 5.0 seconds. Calculate the acceleration of the block.

(c) find the mass of the toy

2. Relevant equations

(a) Do I have to use the frictional force equation to find the answer? (Ffric = μ* F norm)

(b) should I use the net force equation? Fnet=M*A

3. The attempt at a solution

(A)I was considering using the frictional force equation to solve the problem but I don´t have all the variables

(B) Velocity v Time graph perhaps?

thanks for the help (I´m a noob in physics)

2. Jul 25, 2012

### tiny-tim

welcome to pf!

hi inzektor95! welcome to pf!
nope!

you can find the friction force either from the cause or from the result

from the cause, you would need to know the mass and the coefficient of friction … you don't, so that's out!

from the result, you know the acceleration is zero, so you should be able to find the force of friction from the information given

for part (b), again you could find the acceleration either from the cause or from the result …

ues the result … you know the initial velocity the final velocity and the time, so use one of the standard constant acceleration equations

3. Jul 25, 2012

### inzektor95

Thanks for the quick reply :)

For A

how can i find the force of friction using the information given? do i have to use a specific equation?

acceleration = 0
velocity = 1.0 m/s
force = 0.50N

For part B

Vi (initial)= 1.0 m/s
Vf (final)= 2.0 m/s
T = 5.0 s
A = ?

so in other words, I should use this equation?
Vf = Vi + at

thank you very much tiny-tim! :D

4. Jul 25, 2012

### tiny-tim

hi inzektor95!
if the acceleration is 0, what is the net force?
yup!

5. Jul 26, 2012

### inzektor95

thank you very much tiny tim