Discussion
A car’s engine has died, and the car is slowing down as it coasts. What may we conclude about the forces acting on the car?
*This question is included in 03. Laws of Motion, question #3
| (A) | There are no forces acting on the car. |
| (B) | ... |
| (C) | ... |
| (D) | ... |
| (E) | ... |
| (F) | ... |
The solution is
Posted: 07/14/2013 18:41
Can you explain why the force is in the opposite direction?
Posted: 07/15/2013 13:51
Hi there. If the force is in the direction the car is going, then the car would be accelerating, not decelerating (slowing down). Recall Newton's law F = m*a. Since car is decelerating, a is a negative number. Since m is > 0, F is a negative number too. Remember that F is a vector, so it it pointing against the positive direction of the mass.