Frictional Force issue

  • #1

Homework Statement


You pull on a 30 kg box with a horizontal force of 110 N to the right. (i) If there are no other forces acting on this box, what is the resulting acceleration? (ii) If the resulting acceleration of the block is only 1.6 m/s, what is the magnitude and direction of the frictional force acting on the block


The Attempt at a Solution


For (i) a- f/m and I got a=3.67

i have no idea how to solve for (ii) i thought it would f=m times a, but i have no idea where to start/solve any help, please?
 

Answers and Replies

  • #2
35,268
11,537
i thought it would f=m times a
You know m and a, so you can calculate F, the net force acting on the block. This net force has two components.
 
  • #3
so f= 30 x 1.6=48
110-48=62N
correct ?

subtract because it moving in the negative direction, right?
 
  • #5
im also stuck on static frictional force question

The static co-efficient of friction between a football blocking sled (90 kg) and grass is 0.56. (i) If an80 kg coach stands on top of the blocking sled, what is the maximal static frictional force?

any hints on the formula to apply?
 
  • #6
35,268
11,537
Which formulas do you have for (maximal) static friction?
 
  • #7
i do not, i was curious to find out which one to use?

do i have to find the net force?
 
  • #8
35,268
11,537
i do not, i was curious to find out which one to use?
There should be exactly one.
do i have to find the net force?
You have to find the maximal force before block+trainer start to move.
 
  • #9
i have fs(max) = c0efficient of static friction x normal force x 9.81
 
  • #10
35,268
11,537
normal force x 9.81
That part is not correct, even if you add the missing units.
 

Related Threads on Frictional Force issue

  • Last Post
Replies
5
Views
871
  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
2
Views
558
  • Last Post
Replies
1
Views
830
Replies
1
Views
2K
  • Last Post
Replies
4
Views
1K
Replies
3
Views
12K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
2K
Top