em assinment 4

8/4/2019 EM Assinment 4

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Department of Mechanical Engineering, MITS-FET Name:

Engineering Mechanics (ME-105) Tutorial. Batch:

Autumn Semester 2011-2012 Roll No.:

Engineering Mechanics (ME 105)

TUTORIAL SHEET-4

1 Define the term friction.

2 Explain the following terms.

a) Coefficient of friction b) angle of frictionc) angle of repose d) cone of friction

3 Block A of mass 12 kg and block B of mass 6 kg

are connected by a string passing over a

smooth pulley. If coefficient of friction is 0.12

at all surfaces of contact find smallest value of

force P to maintain equilibrium.

4 Can the system in figure be in static

equilibrium in the position shown? The

uniform bar AB weight 500 N and the weight

of block c is 300 N. Friction at A is negligible,

and coefficient of static friction is 0.4 at theother two contact surfaces.

5 Determine the minimum horizontal force P

required to hold the crate from sliding down

the plane. The crate has a mass of 50 kg and

the coefficient of static friction between the

crate and the plane is ms = 0.25.

6 Crates A and B weigh 200 N and 150 N,

respectively. They are connected together

with a cable and placed on the inclined plane.

If the angle is gradually increased, determine

when the crates begin to slide. The

coefficients of static friction between the

crates and the plane are mA = 0.25 and mB =

0.35.


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7 Determine the distance s to which the 90 kg

painter can climb without causing the 4 m

ladder to slip at its lower end A. The top of the

15 kg ladder has a small roller and at the

ground the coefficient of static friction is 0.25.

The mass center of the painter is directly

above his feet.

8 The man in Fig. is trying to move a packing

crate across the floor by applying a horizontal

force P. The center of gravity of the 250-N

crate is located at its geometric center. Does

the crate move if P =60 N? The coefficient of

static friction between the crate and the floor

is 0.3.

9 The uniform stone in Fig. has a mass of 500 kg

and is held in the horizontal position using a

wedge al B. If the coefficient of static friction is

= 0.3 at the surfaces of contact. Determine the

minimum force P needed to remove the

wedge. Assume that the stone does not slip at

A.

10 Determine the smallest horizontal force P

required to lift the 200-kg crate. The

coefficient of static friction at all contacting

surfaces is 0.3. Neglect the mass of the wedge.


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11 A flexible cable which supports the 100 kg load

is passed over a fixed circular drum and

subjected to a force P to maintain equilibrium.

Value of between the cable and the fixed

drum is 0.3. (a) For =0, determine the

maximum and minimum values which P may

have in order not to raise or lower the load.

(b) For P=500 N determine the minimum value

which the angle may have before the loadbegins to slip.

12 A 80 kg farmer tries to restrain the cow from

escaping by wrapping the rope two turns

around the tree trunk as shown. If the cow

exerts a force of 1100 N on the rope,

determine if the farmer can successfully

restrain the cow. The coefficient of static

friction between the rope and the tree trunk is

0.15 and between the farmers shoes and the

ground.

em assinment 4

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