11th Class Chapter two Physics Short Questions

Mention the criterion for positive and negative torque.

Positive torque: Anti-Clockwise torque is taken as positive.

Define null and equal vectors.

Null vector: A vector of zero magnitude and arbitrary direction is called null vector.

Two vectors have unequal magnitude. Can their sum be zero? Explain.

No, the sum of two vectors having unequal magnitudes can't be zero. The sum of two vectors will be zero only when their magnitudes are equal and they act in opposite direction.

Is it possible to add a vector quantity to a scalar quantity?

No it is not possible to add a vector quantity to a scalar quantity because the physical quantities of same nature can be added. Vectors can be added to vectors and scalars are added in scalars,but the vectors can't be added to scalar.

Can a vector have a component greater than the vector's magnitude?

No' the magnitude of the component of a vector can never be greater than the vector's magnitude. The maximum value of magnitude of component can be equal to the magnitude of the vector.

Define unit vector.How we find it?

A unit vector in a given direction is a vector with magnitudes one in that direction.Its is used to represent the direction of a vector.

Two vectors have unequal magnitude.Can their components be equal in magnitude?

No, the components of two vectors cannot be equal in magnitude if the two vector have unequal magnitudes.

Why can a vector not have a component greater than the vectors magnitude?

The magnitude of the components of a vector can not be greater than the vectors magnitude because component is always a part of the resultant vector. This relation show that if any two components of a vector are zero then the magnitude of the third components may be equal to the vectors magnitude but it can never be greater.

Can you add zero to a null vector?

No, zero can't be added to a null vector because zero is a scalar and scalars can't be added to vectors Only the physical quantities of same nature can be added.

How would the two vectors of the same magnitudes have to be oriented,if they were to be combined to give a vector of the same magnitude?

The two vectors of equal magnitudes are combined to give a resultant vector of same magnitude when must be oriented at an angle of 120⁰ With each other.

Define the term unit vector.

Vector having the unit magnitude is called the unit vector. It is used to indicate the direction of a given vector.

Differentiate between static and dynamic equilibrium.

Static Equilibrium: If a body is at rest, then it is said to be in static equilibrium.

What are rectangular components of a vector?

The components of a vector which are perpendicular to rectangular components.each other are called

Explain rectangular coordinates system.

Two lines drawn at right angles to each other are know as coordinate axes and their point of intersection is known as origin. This system of coordinate axes is called rectangular coordinate system.

Discuss the multiplication of a vector by a number?

We can multiple a vector by a number. If the number is positive, then the direction of given vector and product vector will remain the same. If the number id negative, then the given vector and product vector will be acting in opposite direction.

You are falling off the edge.What should you do to avoid falling?

You should bend yourself backward to avoid falling off the edge.Because of this center of gravity will shift backward.

State condition of rotational equilibrium.

The vector sum of all torque acting on any object must be zero.

Can a body rotate about its center of gravity under the action of its weight?

No a body cannot rotate about its center of gravity under the action of its weight.Because the whole weight of the body acts on its center of gravity. The moment arm is zero in this case .

Write down the steps for addition of vectors by rectangular components method.

Discuss the condition of equilibrium?

There are two condition of equilibrium which are given below.First Condition of equilibrium:According to the first condition of equilibrium, a body is said to be in equilibrium, if the vector sum of all external forces acting on the body is zero they cancel the effect of each other { F = 0In the component form we haveF1y+ F2y + F3y +................ +Fny =0Fy = 0A book lying on the table and paratrooper moving down words with uniform Velocity satisfies the first condition of equilibrium.Second Condition of Equilibrium:According to the condition of equilibrium, a body is said to be in equilibrium on a body is equal to zero.{ T = 0Explanation:There are certain situation in which on extended body will not be in equilibrium even when the first condition of equilibrium is satisfied. For Example, in the two equal forces are acting on a meter rod in opposite direction. As the line of action of these forces are not the same so the meter rod do not remain in state equilibrium and begins to rotate in anti clock wise direction. So the first condition of equilibrium is not sufficient in such a case Under such situations we should arrange the forces on the body in such a way, htat they causes clock-wise torque and anti-clock wise torque acting on the body simultaneously and cancel the effect other.

What are rectangular components of a vector?

The components of a vector which are perpendicular to each are called rectangular components.

Under what circumstances would a vector have components that are equal in magnitude?

Define position vector and resultant vector.

Position Vector: A vector which describes the location of a point with respect to origin is called position vector.

Define the following?

Parallel Vectors:Vectors are said to be parallel to each other if they are acting in the same direction.

Why can a body not rotate about its centre of gravity under the action of its weight?

As we know that the centre of gravity is that point at which the whole weight of the body acts.In this case, the line of action of force (weight) passes the pivot point (centre of gravity).Therefore, moment arm is zero.As a result torque is also zero.

Two vector of magnitude 10 each making angle 180^o With each other.Find the magnitude of their resultant.

We know that the sum of two vectors which are equal in magnitude and opposite in direction is zero.

Define unit vector?

A vector whose magnitude is one is known as unit vector

Write down the condition for a body to be in complete equilibrium.

Write two examples of vector product.

Define equilibrium ?

Equilibrium:The state of a body, under the action of several forces acting together and there is no change in the translation motion as well as its rotational motion is known as equilibrium.

Define null vector and component of a vector.

Null Vector is a vector of zero magnitude and arbitrary direction.

When body is in .

Give two conditions of equilibrium.

Define Physical quantities & Magnitude?

Physical Quantities:Those quantities which can be measured are known as physical quantities. For example, length, mass, temperature, speed, velocity, acceleration, energy , torque etc.

What are coplanar and concurrent forces?

All the forces lying in the same plane are called coplanar forces.

DIscuss the addition of vectors by graphical Method or geometrical Method?

We can add two or more than two vectors by geometrical method or graphical method to get their resultant vector. we use "Head-to-Tail rule for addition of vectors by graphical method or geometrical method.

What do you mean by concurrent force ? Explain with examples ?

Concurrent Force:Two or more than two force are said to be concurrent force, If they are acting upon a body and their lines of action passes through a common point.Explanation:Consider a bulb which is suspended by means of a thread from a rigid support In this case the weight 'w' of the bulb is acting in down wards direction while the tension 'T' in the thread is acting of both forces passes through the same point or common point. Both forces balance each other and as a a result the bulb remain the state of equilibrium such force are know as concurrent forces.

Define and explain position vector ?

What is the moment of a force about the point lying on the axis of rotation?

What is difference between moment arm and moment of force?

Define scalar and vector quantities?

Scalar Quantities:Those quantities which are completely specified by their magnitude only, are known as scalar quantities. For example Speed, Mass, energy, work, power.

Define torque.Write its units and dimensions,

Define and explain the scalar product?

Explain with the help of an example what is the rang of possible values of the resultant of two vector ?

Discuss, how a vector is represented?

A vector is usually represented by the following two method.

Define and explain the resolution of a vector ?

Discuss the addition of vector by rectangular component method?

The resultant of two vector, one is double in magnitude than the other, perpendicular to the smaller force. What is the angle between the two forces ?

Discuss the commutative property of addition of vectors ?

Define and explain vector product ? (or) Cross Product.

Discuss the subtraction of vector ?

Explain why do buses and heavy trucks have large steering wheels ?

We know that the magnitude of torque depends upon the moment arm and applied force T = r* f

Define Torque (or) Moment of force?

The turning effect produced in a body about a fixed point due to an applied force is known as torque (or) Moment of force.

The gravitational Force acting on a satellite is always directed towards the centre of the earth?

We known that the torque depends upon the moments arm and applied force. Mathematically we have

What is the minimum number of unequal vector in to a null vector?

The minimum number of unequal vector to result in to a null vector must be three. If we add three vector of unequal magnitude in such a way that they forms the sides of a triangle, then their resultant must be zero.

A point object acted on by forces 4N, 5N, and 6N is in equilibrium. If 6N force is removed, what is the resultant force on the object ?

What is the minimum number of unequal vector in to a null vector?Explain

The minimum number of unequal vector to result in to a null vector must be three. If we add three vector of unequal magnitude in such a way that they forms the sides of a triangle, then their resultant must be zero.

Explain how cranes are able to light very heavy load without toppling ?

We know that object with a high centre of gravity are likely to be unstable . For this reason, the bases of the cranes are made low and heavy, so that centre of gravity remains low.