# Scrambler friction problems

1. Mar 30, 2004

### pineapple629

we need to find the friction of our car after we launch it. it rolls to a stop at 10 meters.

http://home.comcast.net/~jay7042/physics.bmp

initial velocity after it laucnhed is 1.25 m/s
distance traveld 10m in 7s
we need to find the friction and efficiency of the car

Last edited by a moderator: Apr 20, 2017
2. Mar 30, 2004

### Chen

Use energies. The only non-preserving force that operates in the system is the friction, and its work is equal to the change of mechanical energy of the whole system:
$$W_f = \Delta E_m = (\Delta E_k) + (\Delta E_p)$$
$$-fX = (0 - 0) + (0 - mgh) = -Mgh$$
Where M is the mass of the weight, and X is the total distance the car travels (1m + 10m), assuming there is also friction in the acceleration area (the 1m inside the structure). If there is no friction in that segment, then X is just 10m.

Last edited: Mar 30, 2004
3. Mar 30, 2004

### pineapple629

we are only going to calculate the 10m after it launched. i plugged my numbers into the bottom equation as best as i could and got -.023*10 = (-.178*9.8*1) = 1.97 now im confused what 1.97 is

4. Mar 31, 2004

### Chen

Where did you come up with 0.023N as the friction force? I thought that's what you were going to find.
$$-fX = -Mgh$$
Therefore:
$$f = \frac{Mgh}{x} = \frac{2kg10\frac{m}{s^2}1m}{10m}$$