I am trying to understand net force intuitively and this is what I think.
If a net force is towards the positive $x$ direction, which of the following is true ?
a) It can be moving in the negative $x$ direction
b) It can be speeding up
c) It can be slowing down
d) It can be moving in the positive $y$ direction
a) No, because if an object is moving towards the left, $x_f-x_i$ is negative, so the velocity is negative as well as the acceleration. So, impossible.
b) Yes. as a matter of fact it has to because positive acceleration means speeding up.
c) No. Same reason as b.
d) No, because the y-direction is perpendicular to the x.
I got this problem wrong and I don't think I am really understanding acceleration. Can someone help me out ?
Best Answer
then the $x$ component of velocity of the object is increasing; period.
Now, knowing this, are any of the statements (a) through (d) true?
Sure, it could be moving in the negative $x$ direction. All that is required is that the velocity is becoming less negative (increasing), i.e., that the acceleration is in the positive $x$ direction.
Sure, speed is the magnitude of the velocity. So, it could be speeding up if it were moving in the positive $x$ direction.
Sure, speed is the magnitude of the velocity. So, it could be slowing down up if it were moving in the negative $x$ direction.
Sure and this motion would be completely unaffected by the net force in the positive x direction.
Acceleration is the rate of change in velocity. If one tells you that the velocity is changing but doesn't specify what the velocity is, you don't know anything about the velocity, only its rate of change.