# Question #99b49

Aug 29, 2016

The car is accelerating to the right at $0.9 \frac{m}{s} ^ 2$
It is impossible to say which direction the car is moving. We know only that the velocity of the car is changing.

#### Explanation:

Unless you were given a more complete description about the range of possible motions to consider, this question is very poorly designed.

Using Newton's laws we know that:
$F = m a$

Or, since we know the force and the mass, the thing we can solve for is the acceleration:
$a = \frac{F}{m}$

Assume that gravity and the normal force cancel each other as they usually do.

$a = \frac{9000 k g}{10000 N} = \frac{9}{10} \frac{m}{s} ^ 2$

The diagram drawn in the problem is not how I would have interpreted the question. A force from the left will tend to accelerate an object toward the right. In the force diagram, this would be represented by a force arrow on the right. Notice how this is similar to the normal force which is provided by the ground but is drawn extending upward from the object.

If we assume that the car is forward moving at a constant velocity on a simple curve in the road, then a force from the left indicates that we are turning to the right.

If the car were moving in reverse, it's still making a curve to the right. But the direction is very different.

If the car is in a skid it may be sliding sideways with no forward motion. In this case the car is moving directly to the left. Imagine if you were driving along and suddenly lost control wound up sliding down the highway with your car perpendicular to the traffic lane (with the left side of the car leading). The friction of the tires would be exerting a force from the left side. But your motion would be in that same direction.

Even as the car comes to a stop there may still be a force. (However, with friction this doesn't tend to be constant through zero velocity.) But, technically, the car may not be moving at all.