- #1

Clara Chung

- 304

- 14

## Homework Statement

A block of mass 5 kg rests on a wedge placed on a table. The mass of the wedge is 10 kg. The wedge has an incline of angle θ = 30 degrees.

a) Find the normal reaction of the table acting on the wedge.

ANS : 150N

b) Repeat (a) if the block slides down the wedge without friction. The wedge remains stationary all the time.

ANS : 138N

c)Repeat (a) if there is a friction of 10 N between the block and the wedge surfaces. The wedge still remains stationary.

ANS : 143N

## Homework Equations

F= ma

## The Attempt at a Solution

I have no problem with (a), it is simply (5+10)x10 = 150N

But starting from (b), I have no ideas. I don't know how to obtain the net force when it is inclined by 30 degrees. I tried to separate 50N into 2 components, the component parallel to the surface of the wedge is canceled out. Only the component perpendicular to the surface remains. Then I separate it to 2 components again, and take the component perpendicular to x-axis into account. So it is 50 x cos 30 x cos 30 = 37.5 N, so b= 37.5 +100 = 137.5N. I don't know if my concept is correct or not.

I hope you can teach me b and c part