Homework Help: Finding time and distance with NLM.

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1. Oct 24, 2015

Sace Ver

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

A puck of mass 30 g slides across rough ice, experiencing a frictional force of 0.20N. If it was moving at 10km/h when it hit the ice patch,
(a) how much time did it take to stop?
(b) how long was the ice patch?

Given:
m=30g (0.03kg)
Ff=0.20N
V=10km/h (2.7m/s)

2. Relevant equations
Fnet=ma
a=v/t
v=d/t

3. The attempt at a solution

Fnet = ma
a = Fnet/m
a = 0.20N / 0.03kg
a = 6.6m/s2

a = v/t
t = v/a
t = 2.7m/s / 6.6m/s2
t = 0.40s

v = d/t
d = vt
d = (2.7m/s)(0.40s)
d = 1.08m

So therefore, it took 0.40s for the puck to stop. The ice patch was 1.08m.

2. Oct 24, 2015

Sace Ver

Can someone check it over PLS and thank you!

3. Oct 24, 2015

SammyS

Staff Emeritus
The time is correct. The distance is not correct.

The velocity is not constant, so the average velocity is not 2.7 m/s.

4. Oct 24, 2015

Sace Ver

So would 2.7m/s be the initial velocity and then 0 would be my final velocity?

5. Oct 24, 2015

SammyS

Staff Emeritus
The puck comes to a stop, so yes.

6. Oct 24, 2015

Sace Ver

so it'd be d = 2.16?

7. Oct 24, 2015

SammyS

Staff Emeritus
Yes.

8. Oct 24, 2015

THANK U!!