RogueLeader
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A box of mass 80kg is pulled along a horizontal floor by a rope. The rope is pulled with a force of 100N and the rope is inclined at (20 °) to the horizontal
1. Explain Briefly why the box cannot be equilibrium if the floor is smooth. (In Fact the floor is not smooth and the box is in equilibrium )
2. Calculate The Frictional Force Between The box and the floor and also the normal reaction of the floor on the box The Maximum value of the frictional force between the box and the floor is 120N and the box is now pulled along the floor with the rope always inclined 20° to the horizontal
3. Calculate the force with which the rope must be pulled for the box to move at a constant speed.
4. Calculate the acceleration of the box if the rope is pulled with a force of 140N


i get the first two questions but not the last two. Please help.
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tinkerbella~
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(Original post by RogueLeader)
A box of mass 80kg is pulled along a horizontal floor by a rope. The rope is pulled with a force of 100N and the rope is inclined at (20 °) to the horizontal
1. Explain Briefly why the box cannot be equilibrium if the floor is smooth. (In Fact the floor is not smooth and the box is in equilibrium )
2. Calculate The Frictional Force Between The box and the floor and also the normal reaction of the floor on the box The Maximum value of the frictional force between the box and the floor is 120N and the box is now pulled along the floor with the rope always inclined 20° to the horizontal
3. Calculate the force with which the rope must be pulled for the box to move at a constant speed.
4. Calculate the acceleration of the box if the rope is pulled with a force of 140N


i get the first two questions but not the last two. Please help.
3) Use the fact that the force pulling the rope must equal the frictional force for the box to move at constant velocity. From F=ma, resultant force must be 0 if a=0.

4) Again: F=ma. Find the resultant force, you're given the mass.
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aamirac
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I think they are a case of F=ma
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username1162972
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(Original post by tinkerbella~)
3) Use the fact that the force pulling the rope must equal the frictional force for the box to move at constant velocity. From F=ma, resultant force must be 0 if a=0.

4) Again: F=ma. Find the resultant force, you're given the mass.
What if it doesnt. What if f=ma dnt work. Then what u gna do b


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tinkerbella~
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(Original post by physicsmaths)
What if it doesnt. What if f=ma dnt work. Then what u gna do b


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Cry and give up on both mechanics and life, everything you know is a lie.
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Username002
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It's Newtonian mechanics F=ma is always the answer.
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username1162972
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(Original post by Username002)
It's Newtonian mechanics F=ma is always the answer.
Otherwise we use cons of momentum for variable masses. M5 Ch 2


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TeeEm
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(Original post by physicsmaths)
Otherwise we use cons of momentum for variable masses. M5 Ch 2


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