Question

3) If an object moves with a constant velocity, we can conclude that
a. it is moving toward its natural place.
b. there are no forces acting on it.
c. there is no unbalanced (net) force acting on it.
d. it has a very large mass.
C?

Answer 1

Constant velocity means that it is not accelerating.
\[\sum F = ma\]

If a is zero, then the sum of all forces is zero.

So, yes, you are exactly correct :)

Answer 2

Cool.... can I ask you another question?

Answer 3

sure

Answer 4

Assume that you are driving down a straight road at constant speed. A small ball is tied on the end of a string hanging from the rear view mirror. Which way will the ball swing when you apply the brakes?
a. forward.
b. backward.
c. It will not swing forwards or backwards.
d. It depends on how hard you apply the brakes.
yeah, i'm a little clueless on this one

Answer 5

Think of inertia. You are slowing down. Will the ball slow down at the same rate?

Answer 6

No? Well not at the same rate sine inertia is like resistance or something like that!??

Answer 7

Since* Typo!

Answer 8

Right. The string has to pull the ball backwards to slow it down with the car.

Since initially the car is slowing down, but the ball isn't, which way does the ball appear to move inside the car?

Answer 9

Forwards?

Answer 10

Yep!

Answer 11

Alright.... there is one more question that i did not understand:
An object is pulled to the right with a force of 10 N and to the left with a force of 15 N. The net force on the object is
a. 25 N to the left
b. 25 N to the right
c. 5 N to the left
d. 5 N to the right
e. none of the above
Would it 5 left since its 5 more powerful? Idk

Answer 12

Exactly.

Since the forces are directly opposite one another, we just take the difference between them.

Answer 13

Ok just out of curiosity, what if the forces were not directly opposite???

Answer 14

You'd have to "decompose" them into vector components, and then cancel the terms that are directly against one another.

Answer 15

Ok, thank you for your help!

Answer 16

For instance:

You push to the right, parallel to the ground, with 15N. I push downward at a 45 degree angle with a force of 20N. Who wins? (Assume the floor is solid and won't give out, and that the box starts at rest).

Well, my force needs to be "decomposed" into x and y components. We don't really care about the y component, since that pushes into the ground, but for the sake of completeness, I'll show it:
\[F_x = (20 N)Cos(45^o)\]
\[F_y = (20N)Sin(45^o)\]

So the net force in the x-direction would be:
15 - 20Cos(45)

If this is a positive quantity, you win and the box moves to the right.
If it's negative, I win and the box moves to the left.
If it's zero, then the box doesn't move.