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- Homework Statement
- Referring to Fig. 5-4: What horizontal force F must be constantly applied to M=21kg so that m1 = 5kg does not move relative to m2 = 4 kg. Neglect friction.

- Relevant Equations
- ...

g=9.81

m2g=m1a,

a=(m2/m1)g=0.8g

F=0.8g x (M+m1+m2)= 0.8g x (21+5+4)= 0.8g x 30= 235.44 N.

The answer key however indicate that the answer is 392N. This made me think that the tilt of m2 has something to do with it, but I can't see how much it will make F larger than the above answer.

m2g=m1a,

a=(m2/m1)g=0.8g

F=0.8g x (M+m1+m2)= 0.8g x (21+5+4)= 0.8g x 30= 235.44 N.

The answer key however indicate that the answer is 392N. This made me think that the tilt of m2 has something to do with it, but I can't see how much it will make F larger than the above answer.