# Find the acceleration of the object

TyErd
This questions really frustrating me

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Homework Helper

You can find the acceleration of the object by using
vf^2 = vi^2 + 2*a*s. vi and s is given. Find a.
This acceleration has two components. One the component of g which acts in the downward direction. And the other due to braking force, which acts in the opposite direction of the motion. In the diagram sinθ is given. (10/100).
Write down the expression for the acceleration and solve the problem..

TyErd

um to find acceleration cant you use a=gsinθ, but if you use that its 10xsin(5.740) which equaks 1.001 because if sinθ=10/100 then θ=5.74. However if I use your equation i get a=4.5m/s/s

Homework Helper

um to find acceleration cant you use a=gsinθ, but if you use that its 10xsin(5.740) which equaks 1.001 because if sinθ=10/100 then θ=5.74. However if I use your equation i get a=4.5m/s/s
The acceleration a is correct.
Now a = af - g*sinθ, where af is the acceleration due to frictional force.

TyErd

how do i calculate af?

Homework Helper

how do i calculate af?
In the problem they have asked
What is the constant braking force?
So you have find af, then the braking force = m*af.
You have found a and g*sinθ. Using the above equation find af.

TyErd

so is af = 4.500 - 1.001?, then the braking force is 1000*3.499=3499???????????????

TyErd

so then what is the driving force?

TyErd

is it just 1000N?

Homework Helper

so is af = 4.500 - 1.001?, then the braking force is 1000*3.499=3499???????????????
This step is wrong.
af = a + g*sinθ.
Αnd what do you mean by driving force?
Sledge moves down due to gravitational force. The frictional force stops it.

TyErd

whats the difference between a and gsinθ?

Homework Helper

whats the difference between a and gsinθ?
mg*sinθ ......> Force acting on the sledge due to gravity in the downward direction
μ*mg*cosθ.......>Frictional force in the upward direction = m*af
Net retarding force acting on the sledge is
mg*sinθ - m*af = - m*a.

TyErd

ok we calculated before that gsinθ = 1.001. so thats the acceleration downwards direction. then we calculated a to be 4.500 using that equation. why are they different when there both acceleration?

Homework Helper

When you are using the equation vf^2 = vi^2 + 2*a*s. to find a, you are getting the acceleration -4.5 ms^-2. whereas g*sinθ +1. There directions are different.