Question

Please help?
http://oi63.tinypic.com/xpxxlh.jpg

Answer 1

this is not math

Answer 2

I only need help with the first one.

Answer 3

I put it in the physics category didn't I?

Answer 4

yes

Answer 5

Okay. Good. I thought you were saying it ended up in the math category somehow.

Answer 6

why

Answer 7

So on the first one. I get that the static force max should be over 480N since it's not moving.

Answer 8

yes

Answer 9

medal me

Answer 10

But I'm not exactly sure which answer I should be going with.

Answer 11

correct

Answer 12

wait

Answer 13

ok

Answer 14

what grade

Answer 15

This is college stuff.

Answer 16

i think it is the third one

Answer 17

give me a medal if it helped

Answer 18

Could you explain why?

Answer 19

i mean the second one because the force should be weaker if it that thing stoped

Answer 20

I think I selected that one before and it counted it wrong.

Answer 21

Never mind. I didn't.

Answer 22

ok

Answer 23

@staldk3 can you give me a medal and be my fan

Answer 24

Yeah

Answer 25

thanks

Answer 26

np. Thanks for the help

Answer 27

np

Answer 28

i gave you a medal

Answer 29

you became a fan to me

Answer 30

It counted the answer wrong.

Answer 31

how

Answer 32

can you see what the answer is

Answer 33

Don't know.

Answer 34

bye

Answer 35

@ganeshie8

Answer 36

@CShrix

Answer 37

@matt101

Answer 38

@agent0smith

Answer 39

@Data_LG2

Answer 40

Try applying the Friction force formula we used last night.
Fn = Fg =mg

Ff = mui x Fn
Ff = mui x mg

you'll get the amount of static friction force.

Answer 41

596.7423

Answer 42

Okay so that's the 6.0x10^2

Answer 43

So should it be the 2nd to last one on the first question?

Answer 44

Give me a sec. i'm reading them again

Answer 45

Take your time. I only need the first one. I figured out the second one.

Answer 46

okay got it.
analyzing the other choices, you're choice is the best one.
Since the couch didn't move, there are two possible reasons: either the net force is zero (newton's first law) or the applied force is not enough to overcome the frictional foce

Answer 47

**your

Answer 48

@Data_LG2
It could be equal to or stronger than 480 N
is the answer?

Answer 49

i think so

Answer 50

I tried that one and it count it wrong. Because it was what I thought as well.

Answer 51

*counted

Answer 52

@agent0smith

Answer 53

@Whitemonsterbunny17

Answer 54

Also, I wouldn't give people medals just because they ask for it and clearly didn't show the steps for how they "helped." But that's just my opinion.

Let's say I push a couch with a force of F. I have to do two things to determine if it will move.
1). Calculate the frictional force
2). Compare the frictional force to the applied force

If the static frictional force > applied force, then the couch will not move. This is because the force keeping it in place is greater than the force required to make it move. However, if the static frictional force < applied force, then it will obviously move.

Answer 55

But since it's not moving the static force is greater than the applied force

Answer 56

Yes, that is a true statement.

Answer 57

I've chosen
It could be equal to or stronger than 480 N
It is stronger than 480 N but weaker than 6.0 × 102 N
It is equal to 0 N
It is weaker than 480 N
but all of those have been counted wrong.

Answer 58

@CShrix

Answer 59

Remember that when we calculate the static frictional force, we are calculating the maximum force needed to overcome static friction.

Answer 60

If we push with 480N, the static frictional force HAS to be...?

Answer 61

Static friction force can *never* be greater than the applied force - otherwise the object would move in the direction of the friction force. Static friction force can only equal the applied force, up to its maximum value.

Answer 62

It has to be greater than 480N since it's not moving meaning the max is more than 480N

Answer 63

Okay, think of it like this.

I push the box with 480N and the maximum needed to overcome static friction is ~590..
If I push the box, will it start moving backwards? No!

Answer 64

Well actually the applied has to be less than the max. Not the static being greater since the max doesn't change.

Answer 65

Sorry. I worded my answer wrong before

Answer 66

The max doesn't change -- correct.
But if we push a box with 480N, the frictional force is going to be the same until we pass the maximum. Since 480<~590, we already know that the box is NOT going to move. Since it doesn't move, that means for every force <~590, the static friction is going to be equal to the applied force. If the static frictional force was greater than our applied force, then it would start moving backward.

Answer 67

Imagine this -- there is one guy on the left and right sides of a block. The goal for both guys is to keep the box NOT to move... If the left guy pushes with a force of 10N, how much must the guy on the right push? 10N!

Now let's say the guy on the right is weak, and can only handle up to 20N. That means that the guy will push back with any force that the guy on the left pushes that is less than 20. Once the guy on the left pushes with a force higher than 20, then the guy on the right will fail and the box will move!

Answer 68

Right

Answer 69

Okay so the static should equal the applied force.

Answer 70

In our example, the left guy is our applied force, and the guy on the right is static friction. In order to keep the box still, the static friction must be the same as the applied force. But static friction has a maximum "strength" and once the applied force is greater than that of the static friction, then the box will move.

Answer 71

Correct

Answer 72

The answer is
It is equal to 480 N?

Answer 73

Read the above and you tell me!

Answer 74

Well it's not moving. So the max of the static hasn't been reached which means that the 480N isn't strong enough to make the object move. So the static should equal 480N as the applied for is 480N and there isn't any forward or backward motion.

Answer 75

Note that it's irrelevant in this question what the max static friction is. Don't even calculate it.

Because... They TOLD you that when the 480N force is applied, the object is at rest - this means the net force is zero, and that means the static friction must be 480N.

Answer 76

Okay so it is equal to 480N correct?

Answer 77

`that means the static friction must be 480N.`

Answer 78

The object is at rest, so the net force is zero - that 480N force has to be balanced out by an equal and opposite force... so you shouldn't need to question what the static friction force is.

Answer 79

So it isn't equal?

Answer 80

...what? Re-read my last message.

Answer 81

I think you need to take your time and read more carefully.

Answer 82

I think I'm getting myself confused.

Answer 83

Shouldn't the Fs=480N and the Fapplied= 480N
Fnet = 0 because Fnet= 480-480?
That's all right.....right?

Answer 84

Yes. That's exactly what I was saying above.

Answer 85

But that is HOW you know the static friction force is zero.

Fnet = 480 - Fs

You know Fnet is zero because the object is at rest, so

0 = 480 - Fs

Answer 86

So the static is equal to 0?

Answer 87

0 = 480 - Fs

Solve for Fs. What do you get?

Answer 88

480N

Answer 89

Okay then. That's your answer.

Answer 90

Yes. How did you get zero?

Answer 91

Thought you were saying the static was zero.

Answer 92

The sum of the forces is 0 because the box is not accelerating. (not moving)

Answer 93

How?

Answer 94

Okay I thought the fnet are zero

Answer 95

The Fnet IS zero.

Answer 96

hi

Answer 97

so I was right on that part.