DYNAMICS!

[monkeywantsabanana]

Hey guys... as usual... i need some help !

A body of mass 2kg is being pulled up a smooth plane inclined at 20 degrees to the horizontal by a force of 10 N parallel to the plane. Find:

a) the acceleration
b) the distance travelled up the plane from rest in 2s

Any help is appreciated! Cheers!

[b^3]

here is a diagram, typing explanation now

[b^3]

here is a diagram, typing explanation now

[b^3]

I didn't do Dynamics in GMA but I did it in spesh this year, so this should be the same working.

a) resolve forces parallel to plane
10-2gsin(20)=2a
a=5-gsin(20)
a=1.648m/s²
b)u=0m/s
x=?
t=2s
a=1.648m/s²
use x=ut+1/2at²
x=0+1/2*1.648*4
x=13.2m
So it travels 13.2m up the plane

Sorry I don't know why it doubled posted.

[monkeywantsabanana]

Thanks so much.

Just a quick question from it though... you know how you had 10-2gsin(20) = 2a i assume that's from R = ma

so R (resultant force) = 10-2gsin20 why is this? Can you explain what resultant force actually is? Our teacher never really explained it. He just said it's the difference between the opposite forces.

[b^3]

The R in this diagram is the reaction force of the plane pushing back on the weight of the object (at an angle).10-2gsin(20)=ma is yes the resultant force. It is the force up the plane i.e. 10N minus the force down the plane, that is the component of weight that is pushing down the slope (as it is at an angle). This resultant force is equal to ma (as F=ma). The resultant force is the vector sum of all the forces invovled, also known as the net force.

EDIT: 400th post

[pi]

^^Think of it as the net (or total) force in one direction (ie. perpendicular to plane, or parallel to plane, etc.). This means that forces are components of forces in opposite directions can "cancel" each other out to produce a net/resultant force in one direction (or none at all if forces are the same magnitude).


EDIT: totally beaten

[b^3]

Does this make it any clearer? Also sorry, I probably should have used N instead of R as the normal force instead of reaction force.

[monkeywantsabanana]

Thanks all !