Question

A wooden box of bolts has a mass of 250kg and requires a horizontal force of 2100N to slide it along a horizontal wooden surface at a constant speed. It has a coefficient of friction of 0.86.

Answer 1

If the box were to be kept moving constantly at twice this speed what force would be needed to maintain this constant velocity

Answer 2

First, find the normal contact force or N - it is the force that acts opposite to the force applied to the floor and in this case it is its weight.
N=weight=mg=250*10=2500N
Secondly, for a body to move at constant speed, it means that both driving (Fd) and Resistive (R) forces are equal, meaning R=Fd
The R=$N, where $ is the coeffient of friction and your Fd is 2100N

Answer 3

So, FR = 2150?

Answer 4

Frictional force=coefficient of friction*weight=0.86*250*9.8=?

Answer 5

2107N

Answer 6

So, if we keeping increasing the speed, the force never changes?

Answer 7

2107 is greater than 2100N

Answer 8

Ahsome, is your g 10 or 9.8?

Answer 9

9.8

Answer 10

Wait, your answer is 2107

Answer 11

2107-2100=7N makes the body acceleration.not keep constant velocity

Answer 12

Ok. So if we keep increasing the speed, the force doesn't change?

Answer 13

Unless we can consider as rounded to 2100N, because the question announces that that force causes a constant speed, dont you think @shamim?

Answer 14

I would say so. Its probably because i use 9.8

Answer 15

Ya. Frictional force will b equak to 2100N

Answer 16

So g will b less than 9.8. Right?

Answer 17

Isn't it a bit more? 9.81 something

Answer 18

g=9.81 makes frictional force more than 2107N

Answer 19

Guys, I think they have rounded.

Answer 20

Ya rounded

Answer 21

So, having that considered, I say we foollow the momentum's formula: Ft/m=v, meaning if F doubles, v doubles, hence to maintain double the constant speed, the force has to be 2100*2=4200N.

Answer 22

No @Holos

Answer 23

Constant velocity but the value is doubled . Needs 2100N applied force

Answer 24

Frictional force=2100N
Applied force=2100N
Both r ewual n oposit
So cancelled each other

Answer 25

Exactly, @shamim. The velocity is doubled, but the force needed to sustain stays the same, since friction doesn't increase as you increase your speed.

Answer 26

Thanks @shamim and @Hoslos. You guys were really helpful :)

Answer 27

U r most welcome

Answer 28

:). Would you guys be able to help me with another question?

Answer 29

Of course.
But u should ask question in main page

Answer 30

Yah

Answer 31

Yes, whenever I can possibly explain. I am here.

Answer 32

I'l make a new question. See you guys there :)

Answer 33

Anyway the formula will b
F*t=mv-mu
F*t/m=v-u
@Hoslos

Answer 34

And this formula is for changing velocity. Right?
@Hoslos

Answer 35

Yes, but since the v is constant, guess we can use v as the same.

Answer 36

When v is constant u will write
v-u=0

Answer 37

Exactly.

Answer 38

Let us go help Ahsome, shall we? Let us keep warming up!