Friction - Assignment 4

Kota Bharu Polytechnic

Mechanical Engineering Department

Mechanic of Machines 1
Topic 4 – Friction

(Assignment 4)

1.            A force P acting on a block of mass M is positioned q^o incline to the horizontal surface moving with a constant velocity.  Based on the statement above;

i.              Draw Free Body Diagram (FBD) showing the forces acted on the block.

ii.             Derive the equation for coefficient of friction, µ in terms of P and M.

2.            A block of 100 kg is positioned on the 30^o incline surface.  The block is pulled by a force acting 10^o parallel to the incline.  The coefficient of friction is 0.25.

i.              Draw Free Body Diagram showing the forces acted on the block.

ii.             Determine the value of force needed to pull the block sliding up the incline surface.

iii.            Calculate the operational efficiency.

3.            A 50 kg metal block is placed on a plane with 30^o incline from the horizontal surface.  A 300 N which is parallel to the incline surface is acting on the block to move it upward.  Calculate;

i.              The friction force.

ii.             The coefficient of friction.

iii.            The angle of friction.

A force, P is acting on the same metal block from above to hold it from sliding down.  The force P is acting parallel to the plane surface.  The movement of the block is opposite to the force P direction.  Determine;

iv.           The value of force P.

v.            The value of Force P by neglecting the friction.

4.            A box weight 320.6 N is placed on a plane with a tilt of 30^o to the horizontal line.  The box is retained from sliding down the plane by a force of 92 N acting parallel to the plane.

i.              Find the coefficient of friction between the box and the plane.

The box is pulled upward by a force along the plane, find the force if;

ii.             It acts on the surface of plane and get the efficiencies.

iii.            It is the horizontal.

5.            A box weighing 400 N was arrested from the swipe down the inclined plane 30^o by a force 75  N. The forces acting on the parallel with the plane.

i.              Calculate the coefficient of friction that exists between the box and the plane.

The box is then pulled up by a force along the plane. Calculate;

ii.             Force if it acts 23^o to the plane.

iii.                The efficiency of these operations.