# Physics

A 2000 {\rm kg} car traveling at a speed of 13 {\rm m/s} skids to a halt on wet concrete where mu_k = 0.50. How long are the skid marks?

I tried doing this many times and each answer is wrong. Can someone help?

1. 👍 0
2. 👎 0
3. 👁 636
1. Fc = mg = 2kg * 9.8N/kg = 19.6N = Force
of car.

Fc = 19.8N @ 0 deg.(Hor. plane).

Fp = mg*sin(0) = 19.8sin(0) = 0 = Force
parallel with plane.

Fv = 19.6cos(0) = 19.6N = Force perpendicular to plane.

Ff = u*Fv = 0.5 * 19.6 = 9.8N.

Fn = Fp - Ff = 0 - 9.8 = -9.8N = Net
force.

Fn = ma,
a = Fn/m = -9.8/2 = -4.9m/s^2.

d = (Vf^2-Vo^2) / 2a,
d = (0-(13)^2 / -9.8 = 17.2m. = Length
of skid marks.

1. 👍 0
2. 👎 0
posted by Henry
2. Correction:
mass of the car = 2000kg: NOT 2kg.

Fc = 2000kg * 9.8N/kg = 19,600N.

Fp = 19,600sin(0) = 0.

Fv = 19,600cos(0) = 19,600N.

Ff = u*Fv = 0.5 * 19,600 = 9800N.

Fn = Fp - Ff = o - 9800 = -9800N.

a = Fn/m = -9800 / 2000 = -4.9m/s^2.

The remaining calculations are correct
as is.

1. 👍 0
2. 👎 0
posted by Henry
3. Thank you very much!

1. 👍 0
2. 👎 0

1. 👍 0
2. 👎 0
posted by Henry
5. work = change in kinetic energy
friction force X distance = change in KE
-mu_k n x = 0 - 1/2 m v^2
[Remember, friction does negative work)
mu_k m g x = 1/2 m v^2
Simplifying:
x = v^2/(2 mu_k g) = 17.24 m

Notice that in this solution, the mass of the car is not needed.

1. 👍 0
2. 👎 0
posted by CANTIUS

## Similar Questions

1. ### science

A 2000kg car traveling at a speed of 27m/s skids to a halt on wet concrete where μk = 0.20.

asked by james on November 17, 2014
2. ### Physics

I am trying to calculate the distance and speed a van was travelling behind a car when an accident occured in which the van hits the car. I know that the car brakes and skids 24metres, the van behind brakes and skids 6metres. The

asked by Nat on May 15, 2008
3. ### Physics 1

A 1400 kg car traveling at a speed of 34 m/s skids to a halt on wet concrete where μk = 0.50. How long are the skid marks?

asked by Logan on November 12, 2017
4. ### physics

A 1600 kg car traveling at a speed of 31 m/s skids to a halt on wet concrete where uk = 0.60. how long are the skid marks?

asked by mike on October 2, 2010
5. ### Science

#1. Kilometers per hour describes the speed of an object. ture false **** #2. Which of the following reference points would allow you to observe the speed of a car that you are traveling in? a) an airplane flying across the sky b)

asked by Mindy on February 27, 2014
6. ### science

If you were riding on a train, which of the following would look as if it is not moving? the conductor walking by you a building you are passing a flying bird

asked by Anonymous on April 13, 2014

#1. Kilometers per hour describes the speed of an object. ture false **** #2. Which of the following reference points would allow you to observe the speed of a car that you are traveling in? a) an airplane flying across the sky b)

asked by Mindy on February 27, 2014
8. ### Science

2. Which of the following reference points would allow you to observe the speed of a car that you are traveling in? A. An airplane flying acroos the sky. B. A car traveling next to you at the same speed you are traveling. C. A car

asked by Callie on January 13, 2015
9. ### physics

A 1200 kg car traveling north at 14 m/s is rear ended by a 2000 kg truck traveling at 25 m/s. If the truck and car lock bumpers and stick together, what is their speed immediately after the collision?

asked by Katelyn on November 2, 2016
10. ### physics, dynamics

Car A starts from rest at t = 0 and travels along a straight road with a constant acceleration of 2 m/s2 until it reaches a speed of 27 m/s. Afterwards it maintains this speed. Also, when t = 0, car B located 2000 m down the road

asked by siti on January 13, 2011

More Similar Questions