Magnitude of object with constant speed

In summary, in the given physics laboratory experiment, a 6 kg box is being pushed across a flat table at a constant speed of 0.35 m/s by a horizontal force F. The coefficient of kinetic friction is 0.12. The normal force, Fn, is found to be zero because the box is not accelerating vertically. However, to find the weight of the box, the acceleration due to gravity is used. The normal force is then calculated to be 58.86N. To keep the box moving at a constant speed, the pushing force, F, must be equal to the friction force, Ff. Therefore, Ff can be calculated using the equation Ff = μFn, where μ is the coefficient
  • #1
Kamirusen
3
0

Homework Statement


in the physics laboratory experiment, a 6 kg box is pushed across a flat table by horizontal force F. if the box is moving at a constant speed of 0.35 m/s and the coefficient of kinetic friction is 0.12. what is the magnitude of F.


Homework Equations


F=μ*Fn
where
F = friction
μ = coefficient of friction
Fn = normal force

Fn = mass of object * acceleration


The Attempt at a Solution



i solve for Fn first,
Fn = 6 kg * 0 m/s2
and got an answer of zero for normal force... i let the acceleration to be zero because it says that it has constant speed... Is it normal to have a zero normal force?

and then when i solve for the magnitude of friction...
F = 0.12*0
which is zero also... o_O...

i'm not sure if i got a wrong equation, but i think its correct... or if i got some wrong interpretation of the given values that results to zero friction...

My question is, is it a normal thing for an object with constant speed to have a zero friction?
 
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  • #2
Kamirusen said:
Fn = normal force

Fn = mass of object * acceleration
That's not how you find the normal force. Consider the vertical forces acting on the box.
 
  • #3
thanks for reply...

so ill going to consider the acceleration due to gravity of an object with no horizontal acceleration?
 
  • #4
First and fore most, never solve Newton Laws Problems without FBD. Draw the figure and correctly denote the directions in which the forces acts. Use F(net)=Ma along x-y axes. See what happens.
 
  • #5
Kamirusen said:
so ill going to consider the acceleration due to gravity of an object with no horizontal acceleration?
Sure. You'll need it to find the object's weight.

Just because you might use the acceleration due to gravity does not mean the object must be accelerating. Think of the acceleration due to gravity as a measure of the strength of the Earth's gravitational field.
 
  • #6
In this case
##F_N=mg## m = mass, g=gravity, gravity pulls down with 9.81m/s^2 so find normal force
##F_N=6kg*9.81\frac{m}{s^2}=58.86N##
If you're trying to move the body in constant velocity then
##F_{net}=0## because:
##F_{net}=ma##
##F-F_f=ma##
##F-F_f=m * 0##
##F-F_f=0## so friction is equal to pushing force.
so simply find friction ##F_f=\mu F_N## and that's the pushing force
 
  • #7
thanks ! its clearer now... :)
 

What is the magnitude of an object with constant speed?

The magnitude of an object with constant speed is the measure of its size or quantity without taking into account its direction. It is a scalar quantity and is given by the formula magnitude = speed x time.

How is the magnitude of an object with constant speed different from its velocity?

The magnitude of an object with constant speed only considers the numerical value of its speed, while velocity takes into account both the speed and direction of the object. In other words, magnitude is a scalar quantity while velocity is a vector quantity.

Can the magnitude of an object with constant speed change?

No, the magnitude of an object with constant speed remains the same as long as the speed of the object remains constant. It is only affected by changes in speed or direction.

How is the magnitude of an object with constant speed related to its acceleration?

The magnitude of an object with constant speed is not related to its acceleration. Acceleration is the rate of change of an object's velocity, while the magnitude of an object with constant speed only considers its speed and not its velocity.

How can the magnitude of an object with constant speed be calculated?

The magnitude of an object with constant speed can be calculated by multiplying its speed by the time it takes to travel that distance. For example, if an object travels at a constant speed of 20 m/s for 4 seconds, its magnitude would be 80 meters (20 m/s x 4 s = 80 m).

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