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Chapter:

friction

1. What is not condition for equilibrium in free body diagram for calculation of normal forces?

∑Fx=0 ∑Fy=0 ∑Fz=0 ∑F≠0

∑F≠0

For equilibrium in three dimensional system of axis we have all conditions true as, ?Fx=0, ?Fy=0 and ?Fz=0. Also we have summation of forces equal to zero. Which is not a non-zero value.

Hint Answer

2. When body which is applied forces come in stage of limiting friction n body is termed as to come in _______ equilibrium.

Unstable Stable Non-stable Improper Stable

Unstable

As limiting friction is maximum value of frictional forces. Thus if more force is applied to body n body is going to move forward. Because two surfaces are in contact and friction applies at that surface only, resisting motion of surface. Thus name unstable equilibrium.

Hint Answer

3. As we are using vector math to solve for unknown forces in free body diagrams, what is k.i?

0 1 -1 ∞

0

As dot product of only same Cartesian component is unity, i.e. i.i = 1 and j.j =1, rest all remaining dot product will give 0(i.j = 0 and j.k = 0). Cross product of same plane vectors always give zero. This is generally done because normal forces are perpendicular to surfaces of action of friction.

Hint Answer

4. Determine frictional force acting in given figure.

$Determine frictional force acting in given figure.\r\n$

63.9N 60N 43N 83N

63.9N

None.

Hint Answer

5. Determine vertical force acting in given figure.

$Determine vertical force acting in given figure.\r\n$

236N 600n 403N 830N

236N

The net forces acting on body is shown with help of resultant forces. There are two types, first frictional and second is normal. This is because resultant forces have sum of all forces which are acting in direction which is same.

Hint Answer

6. For rolling of body right handed coordinate system means (consider mentioned axis to be positive)?

Thumb is z-axis, fingers curled from x-axis to y-axis Thumb is x-axis, fingers curled from z-axis to y-axis Thumb is y-axis, fingers curled from x-axis to z-axis Thumb is z-axis, fingers curled from y-axis to x-axis

Thumb is z-axis, fingers curled from x-axis to y-axis

As right handed coordinate system means that you are curling your fingers from positive x-axis towards y-axis and thumb which is projected is pointed to positive z-axis. Thus visualizing same and knowing basic members of axis will not create many problems. The right handed coordinate system is universal throughout.

Hint Answer

7. We show net forces acting on belts with help of ______ forces.

Rotational Linear Helical Resultants

Resultants

The net forces acting on body is shown with help of resultant forces. This is because resultant forces have sum of all forces which are acting in direction which is same. Thus resultant forces are used to show net forces acting in body.

Hint Answer

8. The solving for unknown forces in belts requires vector math. So if a vector is multiplied by a scalar in belt system of forces n_________

Then its magnitude is increased by the square root of that scalar’s magnitude Then its magnitude is increased by the square of that scalar’s magnitude Then its magnitude is increased by an amount of that scalar’s magnitude You cannot multiply the vector with a scalar

Then its magnitude is increased by an amount of that scalar’s magnitude

If a vector is multiplied by a scalar n its magnitude is increased by an amount of that scalar?s magnitude. When multiplied by a negative scalar it going to change directional sense of vector. Vector math is unchanged throughout.

Hint Answer

9. In free body diagrams involving wedges we have use of vector math, so for two vectors A and B, what is A.B (if y have angle α between m)?

|A||B| cosα |A||B| √(|A||B|) cosα |A||B| sinα

|A||B| cosα

The dot product of two vectors is always product of magnitudes of two forces and cosine of angle between m. We need to consider triangle and n accordingly apply trigonometry. This is one of ways of resolving components.

Hint Answer

10. In calculations involving collar bearings and pivot bearings, we use cross product. In that mamatically, for two vectors A and B of any magnitude, cross product of both, i.e. AxB = given by:

|A||B|sinØ |A||B| |A||B|cosØ |A||B|sin(180°+Ø)

|A||B|sinØ

The cross product of two vectors gives a vector which is perpendicular to both of vectors. And mamatic equation for same is given by: |A||B|sin�. And dot product of same by any of or two vectors will give answer zero, as perpendicular. The cross product is same for all systems of its application.

Hint Answer

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All Chapters

View all Chapter and number of question available From each chapter from Engineering-Mechanics

Force Vectors

Equilibrium of a Particle

Equilibrium of a Particle

Force System Resultants

Force System Resultants

Equilibrium of a Rigid Body

Equilibrium of a Rigid Body

Structural Analysis

Structural Analysis

Internal Forces

Internal Forces

Friction

Centre of Gravity and Centroid

Centre of Gravity and Centroid

Moments of Inertia

Moments of Inertia

Principle of Virtual Work

Principle of Virtual Work

Topics

This Chapter friction consists of the following topics

Friction

What is not condition for equilibrium in free body diagram for calculation of normal forces?

When body which is applied forces come in stage of limiting friction n body is termed as to come in _______ equilibrium.

As we are using vector math to solve for unknown forces in free body diagrams, what is k.i?

Determine frictional force acting in given figure.

$Determine frictional force acting in given figure.\r\n$

;

Determine vertical force acting in given figure.

$Determine vertical force acting in given figure.\r\n$

;

For rolling of body right handed coordinate system means (consider mentioned axis to be positive)?

We show net forces acting on belts with help of ______ forces.

The solving for unknown forces in belts requires vector math. So if a vector is multiplied by a scalar in belt system of forces n_________

In free body diagrams involving wedges we have use of vector math, so for two vectors A and B, what is A.B (if y have angle α between m)?

In calculations involving collar bearings and pivot bearings, we use cross product. In that mamatically, for two vectors A and B of any magnitude, cross product of both, i.e. AxB = given by:

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