Find Force Acting on 5.0kg Stone in 20m Distance

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In summary, the conversation discusses a 5.0-kg stone being pushed onto a horizontal surface with a speed of 2.0 m/s and coming to rest after moving a distance of 20 m. The average frictional force acting on the stone is calculated to be 0.5 N, based on its slowing down rate and the force needed to produce this acceleration. The relevance of the initial push and the alternative method using energy are also mentioned.
  • #1
StephenDoty
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A 5.0-kg stone is pushed out onto a level horizontal surface with a speed of 2.0 m/s. If
it comes to rest after moving a distance of 20 m, the average frictional force acting on
the block must have been...?

Since it slows down the fk is > than the Fpush.

Fnet= fk-fpush
ma = umg - fpush
ma + fpush = fk

vf^2= v0^2 + 2as
0= 4 + 40a
-4/40 = a = -.1m/s/s

So the stone is slowing down .1m/s every second which will take 20s.

Since the a = -.1m/s/s and f=ma
then wouldn't the fk = 5*-.1= -.5N
Or would you do fk=mg= 5*9.8= 49N

Any help would be great. Thank you.

Stephen Doty
 
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  • #2
StephenDoty said:
Since it slows down the fk is > than the Fpush.

Fnet= fk-fpush
ma = umg - fpush
ma + fpush = fk
No. The push that set the stone moving is irrelevant. All that matters is that somehow the stone is moving at the given speed and begins to slow down. The only force acting on the stone is friction.

vf^2= v0^2 + 2as
0= 4 + 40a
-4/40 = a = -.1m/s/s
This is good!

What must the force equal to produce this acceleration?
 
  • #3
So fk = 5*-.1= -.5N
right?
 
  • #4
Right. The average friction force is 0.5 N.

(If you are familiar with energy methods, you can solve this problem that way as well.)
 

Related to Find Force Acting on 5.0kg Stone in 20m Distance

1. How do you calculate the force acting on a 5.0kg stone in a 20m distance?

To calculate the force, we use the formula F = m x a, where F is the force, m is the mass of the stone, and a is the acceleration. In this case, since the stone is not moving, the acceleration is equal to 0. Thus, the force acting on the stone would be 0 Newtons.

2. Is there a specific unit for the force acting on the stone?

Yes, the unit for force is Newtons (N).

3. What information do we need to calculate the force acting on the stone?

To calculate the force, we need to know the mass of the stone and the acceleration it is experiencing.

4. Can the force acting on the stone change if the distance is increased?

Yes, the force acting on the stone can change if the distance is increased. This is because the acceleration of the stone may also change, which would affect the overall force.

5. Can you use the same formula to calculate the force acting on objects with different masses and distances?

Yes, the formula F = m x a can be used to calculate the force acting on objects with different masses and distances. However, the acceleration may vary depending on the object's motion and the distance between the objects.

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