Determine the force, Mechanical Engineering

Determine the force:

Determine the force P needed to start block B illustrated in Figure moving to the right if the coefficient of friction is 0.3 for all surfaces of contact. Block A weighs 80 N and block B weighs 160 N.

1930_Determine the force.png

Solution

Figure illustrates the free body diagrams for block A and block B. As the possible motion of the block B is towards right, the direction of frictional forces FA & FB are illustrated acting towards left, for block B. While block B moves towards right the relative motion of block A shall be towards left and therefore the frictional force FA for block A is illustrated acting towards right.

Now the conditions of equilibrium may be applied to determine the force P.

For Block A

                                        ∑ Fx  = 0

                             ∴ FA  = T cos 30o  = 0.866 T                                       ------------ (1)

 (where, T is the tension in the given cord)

                                            ∑ Fy  = 0

                                  ∴ N A = WA  - T sin 30o

                                              = 80 - 0.5 T                        -------------- (2)

Also                           FA  = μ N A

                     ∴ 0.866 T = 0.3 (80 - 0.5 T)

 

∴ T = 24/1.016            = 23.62 N                             -------- (3)

 For Block B

∴ FA  = 0.866 × 23.62 = 20.45 N

∴ N A  = 80 - 0.5 × 23.62 N

= 68.19 N

∑ Fy  = 0

∴ N B  = N A  + WB

= 68.19 + 160

= 228.19 N                 ---------- (4)

FB  = μ N B

= 0.3 × 228.19

= 68.46 N

∑ Fx  = 0                   ----------------( 5)

∴ P = FA  + FB

= 20.45 + 68.46

= 88.91 N                    ----------- (6)

Thus, a force 88.91 N is needed to move the block B to the right.

Posted Date: 1/28/2013 5:24:32 AM | Location : United States







Related Discussions:- Determine the force, Assignment Help, Ask Question on Determine the force, Get Answer, Expert's Help, Determine the force Discussions

Write discussion on Determine the force
Your posts are moderated
Related Questions
The Supplier/Subcontractor shall submit, for acceptance, their Material Traceability and PMI program and procedures, which shall comply with this specification, prior to the sourci

Axis perpendicular to the vertical plane - tetrahedron: A tetrahedron of side 60 millimeter has its base parallel to the VP, along with an edge of the base inclined at 45 o t

WELDING PROCEDURE SPECIFICATION (WPS)   The purpose of Welding Procedure Specification (WPS) and Procedure Qualification Record (PQR) is to determine that weldment proposed

Compute the diameter of a solid shaft: Compute the diameter of a solid shaft transmitting 150 kW at 25 rpm, if the maximum shear stress in the shaft is not to exceed 70 MPa. C


Molecular Structure The polymers have three distinct arrangements of molecular chain, hence resulting in three structures. In amorphous structure the molecular chain are ar

in concept of continum what is the meaning of upper cure

Question Suppose T 1 and T 2 are independent and identically distributed Exponential variables with common hazard λ. What is the density of T = T 1 + T 2 ? What is the E(T-1

Lean Mixture: It generally ranges from approximately 15 : 1 to 17 : 1. By the use of this fuel, engine runs for higher economy.

(Hydrostatic pressure on curved 3-D surfaces) A shark tank in the aquarium has a hemispherical glass viewing "bubble"  jutting into the water from the side wall. The radius of