Turning...?

Question

Picture the corner of a room. Imagine the corner of a room. Let's say that the left wall leading into the corner is labeled 1, the corner itself is labeled 2, and the right wall leading from the corner 3 (I hate that I can't draw here!). O.K., a cat runs across the floor from 1 to 2 to 3 without increasing or decreasing his speed. He only changes his direction of motion at 2 (the corner). Can we say for sure that a force was exerted on the cat at 2?

a) Yes, there had to be a force on the cat at 2.
b) Not necessarily, since no change in the cat's speed occurred.

The answer is: a. There had to be a force on the cat at 2 (the corner). If there were no force the cat would keep going in a straight line and travel into the wall (let's call that continuation of 1 (the left wall) but on the other side point 4), instead of 3 (the right wall coming out of the corner).

Perhaps someonekicks the unfortunate cat at 2 (the corner) in the direction of a point directly in line with and in front of the corner which we can call 5. The force of the kick turns the cat toward 3 (right wall). Or the cat could have turned itself by pushing on the floor with its feet. However, if the cat were on frictionless ice at 2 (corner) it couldn't muster a turning force. No force, therefore no turn -- a "skidout."

But why didn't the force change the cat's speed? Because it was a sideways force. A force pushing forward makes a thing move faster. A reverse force makes a thing slow down, stop or go backwards. But a sideways force makes a thing turn.

Physicists like to say a force always changes a thing's velocity, but does not always change its speed. What is velocity? Velocity is the "arrow" that represents a thing's motion. Physicists like to call the arrow a vector. If a thing goes faster it gets a new longer arrow. If it goes slower, the result of deceleration or negative acceleration, it gets a new shorter arrow or vector. And if it turns, it gets a new velocity vector which might be just as long as the original one put points in a different direction. That means same speed, but in a different direction. So we see in this example that velocity can change while speed does not.

Get it? If speed changes, then velocity changes -- but does it follow that if velocity changes, speed must also change? No.

Answer 1

Well there was a change of direction. Was it not? Since I heard no 'abracadabra' in the discourse I must insist that a force was present at 2 as the velocity VECTOR has changed direction. Unless of course the cat has a mass m = 0...and since its mass was not zero there had to be a force present a 2. I have a sneaky suspicion that it was the wall at 2,3 that applied a force upon the cat as the cat applied a force upon the wall at 2,3.

Answer 2

well............

F= ma, force equals mass times acceleration.....

and if there is no change in velocity, there is no acceleration

so, the force is zero......

so....

b, not neccesarily, because there is no change in speed

the only force acting on the cat would be weight, and the normal force exerted by the floor