How great is the friction force?

  • Thread starter uwmphysics
  • Start date
I was wondering if someone could help explain this. I dont understand how to calculate the friction force...

So heres the question I'm working on

You are applying a 400-newton force to a freezer full of chocolate chip ice cream in an attempt to move it across the basement. It will not budge. The weight of the freezer (including ice cream) is 1000 N. The friction force exerted by the floor on the freezer is
a. 400 N
b. greater than 400 N but less than 1000 N
c. 1000 N
d. greater than 1000 N

thanks
 

nrqed

Science Advisor
Homework Helper
Gold Member
3,528
178
uwmphysics said:
I was wondering if someone could help explain this. I dont understand how to calculate the friction force...

So heres the question I'm working on

You are applying a 400-newton force to a freezer full of chocolate chip ice cream in an attempt to move it across the basement. It will not budge. The weight of the freezer (including ice cream) is 1000 N. The friction force exerted by the floor on the freezer is
a. 400 N
b. greater than 400 N but less than 1000 N
c. 1000 N
d. greater than 1000 N

thanks
You should start with a free body diagram. What are the forces acting on the freezer? In what direction are they acting? Using the fact that the net force is zero (the acceleration is zero since the freezer is at rest), the answer should then be clear.
 
thank you...good idea. I made the diagram, and it would have an unbalenced force without friction, so i think friction has to be 400 N.

do you think I'm right?
 

nazzard

Gold Member
99
0
Hello uwmphysics,

you are lucky, instead of calculating the movement of blocks you got a freezer full of chocolate chip ice cream :approve:

I assume the applied force is meant to point horizontally at the centre of mass of the freezer (no tilting).

In which direction does the friction force point and where is it's origin? Remember the freezer does not budge while applying 400N.

Regards,

nazzard
 

nazzard

Gold Member
99
0
uwmphysics said:
thank you...good idea. I made the diagram, and it would have an unbalenced force without friction, so i think friction has to be 400 N.

do you think I'm right?
Ha, slow forum for me today. Your answer is correct.
 

nrqed

Science Advisor
Homework Helper
Gold Member
3,528
178
uwmphysics said:
thank you...good idea. I made the diagram, and it would have an unbalenced force without friction, so i think friction has to be 400 N.

do you think I'm right?
Yes. Good job. (I am assuming that the person is pushing *horizontally*, otherwise the answer would be different.

The free body diagram should have 4 forces: a normal force acting upward (due to the floor pushing on the freezer), the weight of the freezer (i.e. the force of gravity, acting downward), the force applied by the person, 400 N to the right (let's say) and a static friction force to the left. Since the net force is zero, the friction force must have a magnitude equal to the force applied by the person.

It is *always* a very good idea to draw a free body diagram!!

Patrick
 

Want to reply to this thread?

"How great is the friction force?" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Top Threads

Top