# Help in some phy problems

#### Sweet Sara

Hi everybody,

I have 3 problems, and I need help to know the steps to solve them =)

Problem N.1 :

P1. In the figure shown below, the coefficient of kinetic friction between the 9 kg block on the surface is 0.3.

(a) Draw the free body diagram for the block (object).
(b) Find the magnitude of the force of friction.
(c) Find the acceleration of the object.
(d) If the system initially at rest, find displacement of the 2kg block after 2 seconds.
http://www.alamuae.com/up/uplong/Problem1117531470314431.gif

..........................................

Problem N.2

P2. Tow forces, given by F1 = (20N , 60ْ ) , and F2 = (15N) directed in the x axis, act on an object to give it an acceleration of magnitude 3 m/s2.

(a) What is the direction of the acceleration?
(b) What is the mass of the object?
(c) If the object is initially at rest, what is its speed after 10 s?
(d) What are the velocity components of the object after 10 s?
...........................................

Problem N.3

P3. A 600 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T1. Cable 2 applies a force upward and to the left at an angle of 37° as shown in the figure below. The tension in cable 2 is T2. What are the tensions T1 and T2?
http://www.alamuae.com/up/uplong/problem2117533441086710.gif

Thanks to All ^___^

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#### Dr.D

You need to make and effort and show some work on these before you can be helped, Sarah. Please post what you have done, and then we can help you.

#### Sweet Sara

Dr.D

First of all, thanks for your responce.

For the fisrt problem:

a) the free body diagram
http://www.alamuae.com/up/uplong/pro-1-freebody117650654032943.gif

b) I don't know the direction of the force of friction, it is ( F sin 30 ) or ... ?

c) I think, F = ma
a = F sin(30) / m

then, I did't know what should I do. -.-

d) at the rest, v(initial) = 0

x = [ v(initial)*t ] + [ 0.5 *a * t^2 ]

but first, I should calculet the acceleration with 2kg.

.................

The second problem:

a) The direction of the acceleration will be with the bigger force. Is this true?

.....

I will continue tomorrow ^^

#### Dr.D

You need to start off by

1) reviewing the rules for drawing FBDs
2) reviewing resolution of forces into components

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