lilpenguin
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11. A parcel of mass 60kg is released from rest on a smooth plane inclined at arcsin3/5, to the horizontal. Find the velocity of the parcel when it ha stravelled 5m down the slope.

I found, invsin 0.6 = 37...

sin 37 * 60 * 9.81,

then put that into a kinematic equation, the one with 2as involved ( i dont have the squared signs so wont write it out) and i got 59ms as answer... when asnwer is 7.67, please help
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Henerz
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The acceleration is \frac{3}{5}g OK?

So,

u=0 ms^{-1}
s=5 m
a=\frac{3}{5}g

And you are finding v

Using v^{2}=u^{2}+2as You do get 7.6720...ms^{-1}

EDIT: You haven't forgoten to square rootm it have you as it is v^{2}=...
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lilpenguin
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Thank you so much That really helped, the only thing i dont understnad is what

Arcsin3/5 means,

i thought it meant, invsin3/5 = the angle size, so i did that, found out Sin angle, and then did what you had done

Why is the acceleration just, g * 3/5, is it not, the inv sin of 3/5 ?
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lilpenguin
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And also,

why do we not include the 60kg?

usually, when finding down the slope

we do,

Sin theta * mass * grav... why do we miss out mass?
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Henerz
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The angle of the slope is \arcsin(\frac{3}{5}) Therefore to find the size of the angle in degrees, you just punch it into your calculator and get 36.86989... degrees. However, to find the force down the slope, you are going to do mgsin(arcsin 3/5) and, clearly, sin of arcsin 3/5 is just 3/5.

Therefore, Force downslope = 3/5 mg
Using F=ma, ma=3/5mg
So, a=3/5g

Acceleration down the slope is independant of mass, and [usually] you only need to consider it when you are dealing with friction or another non-gravity-related force.
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ColinOfEdinburgh
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(Original post by lilpenguin)
Thank you so much That really helped, the only thing i dont understnad is what

Arcsin3/5 means...
It is indeed just another way of saying the inverse sine function, crazy maths people :rolleyes:
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lilpenguin
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haha thank you so much henerzfor the help
also thank you colin :P yes those crazy people!


Ohhhhhhh so the mass cancels out, now i see it, thank you both

Now im trying a question which is the opposite, up a slope, haha, who knows how many days till i complete this one hah! :P
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