Forces acting on a block that is pushed against a wall

AI Thread Summary
To move a block pushed against a wall, the applied force must exceed the frictional force. The calculations show that for upward motion, the force must be greater than 44N, while for downward motion, it must be less than 20N. The discussion concludes that the correct option is likely D based on these conditions. Participants agree that the calculations presented are accurate. Understanding the balance of forces is crucial for determining the block's movement.
MatinSAR
Messages
673
Reaction score
204
Homework Statement
What should be the magnitude of force F so that the object is definitely moving?(Frictional force is equal to 0.5 for each newton of vertical force on the surface.)
A)25 B)30 C)40 D)50
Relevant Equations
##F_{net} =ma##
##f_{s} =µ_sN##
##f_{k} =µ_kN##
Picture of problem:
1677619868908.png


For the object to be moving, it must overcome friction.

##f=0.5*0.6F = 0.3F##
##mg=22N##

Upward motion:
##0.8F>mg+f \rightarrow 0.5F>22 \rightarrow F>44N ##

Downward motion:
##0.8F+f<mg \rightarrow 1.1F<22 \rightarrow F<20N ##

I think correct option is D. Can you please guide me if I'm wrong?
 
Physics news on Phys.org
Your work looks good to me.
 
TSny said:
Your work looks good to me.
Thank you for your help.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top