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1. I don't know how to do this:
A packing case of mass 20kg is being pulled across a rough horizontal floor by a rope which is inclined at an angle of 30o to the horizontal. The tension in the rope is 60N and the packing case has an acceleration of 0.5ms-2 . Calculate the value of the coefficient of friction between the packing case and the floor.

2. (Original post by Rashina)
I don't know how to do this:
A packing case of mass 20kg is being pulled across a rough horizontal floor by a rope which is inclined at an angle of 30o to the horizontal. The tension in the rope is 60N and the packing case has an acceleration of 0.5ms-2 . Calculate the value of the coefficient of friction between the packing case and the floor.

Would you know how to do it if the rope was parallel to the floor? Draw a sketch.....

F=ma, friction = (friction coefficient) x R, R=mass x gravity

(The pulling force) - (The friction force) = mass x acceleration

Because the pulling force is at an angle to the floor you have to split it into the horizontal component (pulling the box along) and vertical component. This will affect the value of R because now
R + (vertical component of pulling force) = mass x gravity.
It also impacts the final calculation because
(The horizontal component of the pulling force) - (The friction force) = mass x acceleration

Posted from TSR Mobile
3. (Original post by gdunne42)
Would you know how to do it if the rope was parallel to the floor? Draw a sketch.....

F=ma, friction = (friction coefficient) x R, R=mass x gravity

(The pulling force) - (The friction force) = mass x acceleration

Because the pulling force is at an angle to the floor you have to split it into the horizontal component (pulling the box along) and vertical component. This will affect the value of R because now
R + (vertical component of pulling force) = mass x gravity.
It also impacts the final calculation because
(The horizontal component of the pulling force) - (The friction force) = mass x acceleration

Posted from TSR Mobile
ok thanks. I got it!

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