Assignment - II

VARDHAMAN COLLEGE OF ENGINEERING

(AUTONOMOUS)

Shamshabad– 501 218, Hyderabad

Engineering Mechanics

Assignment-II

1

Determine the horizontal force P applied to the lower block to just pull it to the right as shown in Fig.3. The coefficient of friction between the blocks is 0.2 and that between the lower block and plane is 0.25, Assume the pulley to be frictionless.

2

Small block of weight 1000N is placed on a 300 incline with a coefficient of friction at 0.25 as shown in Fig.

Determine the horizontal force to be applied for:

i. The impending motion down the plane

ii. The impending motion up the plane

3

Two blocks A and B are connected by a horizontal rod and are supported on two rough planes as shown in figure below. If the weight of block B is 1500 N and coefficient of friction of block A and B are 0.25 and 0.35 respectively, find the smallest weight of block A for which equilibrium can exist.

4

An effort of 200 N is required just to move a certain body up on an inclined plane of angle 15 degrees, the force acting parallel to the plane. If the angle of inclination of the plane is made 20 degrees, the effort required again applied parallel to the plane is found to be 230 N. Find the weight of the body and co-efficient of friction.

5

A pull of 20 N, inclined at 25 degrees to the horizontal plane, is required just to have a body placed on a rough horizontal plane. But the push required to move the body is 25 N. If the push is inclined at 25 degrees to the horizontal, find the weight of the body and co-efficient of friction.

6

A block weighing 100 N is resting on a rough plane inclined 200to the horizontal. It is acted upon by a force of 50N directed upward at angle of 140above the plane. Determine the friction. If the block is about to move up the plane, determine the co-efficient of friction.

7

An effort of 2200 N is required to move a certain body up a 200 inclined plane. The force is acting parallel to the plane. If the angle of inclination is changed from20 degree to 25 degree, the effort required to move the body increases to 2500 N. Find the weight of the body and the coefficient of friction.

8

A uniform ladder of length 10 m and weighing 20 N is place against a smooth vertical wall with its lower end 8 m from the wall. In this position the ladder is just to slip. Determine: (i) The coefficient of friction between the ladder and floor. (ii) Frictional force acting on the ladder at the point of contact between ladder and floor

9

A ladder 5 m long has a mass of 18 kg and its center of gravity is 2.4 m from the bottom. The ladder is placed against a vertical wall so that it makes an angle of 60° with the ground. How far up the ladder can a 72-kg man climb before the ladder is on the verge of slipping? The angle of friction at all contact surfaces is 15°.

10

A uniform ladder of weight 800N and of length 7 m rests on a horizontal ground and leans against a smooth vertical wall. The angle made by the ladder with the horizontal is 600. When a man of weight 600N stands on the ladder at a distance 4m from the top of the ladder, the ladder is at the point of sliding. Determine the coefficient of friction between the ladder and the floor.

11

A ladder 5 meters long rests on a horizontal ground and leans against a smooth vertical wall at an angle 70° with the horizontal. The weight of the ladder is 900 N and acts at its middle. The ladder is at the point of sliding, when a man weighing 750N stands on a rung 1.5metre from the bottom of the ladder. Calculate the coefficient of friction between the ladder and the floor.

12

A block weighing 1500N, overlying a 100 wedge on a horizontal floor and leaning against a vertical wall is to be raised by applying a horizontal force to the wedge. Assuming the coefficient of friction between all the surfaces in contact to be 0.3, determine the minimum horizontal force required to raise the block

13

A 150 wedge (A) has to be driven for tightening a body (B) loaded with 1000 N weight as shown in fig. if the angle of friction for all the surfaces is 140, find the force p which should be applied to the wedge.

14

Find the least value of P required to move the block - Coefficient of static friction for both pairs of wedge = 0.3, Coefficient of static friction between block and horizontal surface = 0.6 as shown in Fig.3

15

In a screw jack the helix angle is α and angle of friction is φ show that its efficiency is maximum when 2 α = 90-φ

1 | Page