# Find the speed of the block as it passed through O

• emma-sky
In summary, a block of wood is projected up a 15* inclined plane with initial speed 4m/s. It comes to rest at point A and the coefficient of friction between the block and the plane is 1/10. The distance between points O and A can be found by using the equations of motion and the forces acting on the block, including friction and weight. The coefficient of friction is used to calculate the acceleration of the block, and the mass of the block is not needed for this calculation.

#### emma-sky

Initially a small block of wood is at a point O on a rough plane inclined at 15* to the horizontal.
The block is projected directly up the plane with initial speed 4m/s.
The coefficient of friction between the block and the plane is 1/10.
The block comes instantaneously at rest at A.

i) Find the distance OA

ii) Find the speed of the block as it passed through O when moving back down the plane.

I would really appreciate it if someone could help me with this question as I've spent around half an hour trying to figure it out.

Many thanks.

Welcome to PF.

Well what do you have so far?

What forces are acting on the block? Maybe if you can find the acceleration on the block you can use simple kinematics to figure the distance of OA?

Thankyou,

I understand there's both friction and the weight of the block acting on the object.

However there is no given mass for the object making it hard to calculate the acceleration as i end up with lots of different letters.

I don't understand how the coefficient of friction can be used within the question either?

Sorry if this is a daft question, mechanics is not my strong subject!

emma-sky said:
Thankyou,

I understand there's both friction and the weight of the block acting on the object.

However there is no given mass for the object making it hard to calculate the acceleration as i end up with lots of different letters.

I don't understand how the coefficient of friction can be used within the question either?

Sorry if this is a daft question, mechanics is not my strong subject!

You know F = m*a = μ*m*g*sinθ right? Who needs the mass?