Two Marks Questions with Answers

Two Marks Questions with Answers

Q.1 Define force.

 Ans. :

Force is a physical quantity that changes or tries to change the state of rest or of uniform motion of an object.

Q.2 Differentiate between particle and rigid body.

Ans. :

Particle is a body which has mass but no dimensions whereas rigid body has both mass and dimensions. Particle can have only translational motion whereas rigid body can have translational as well as rotational motion.

Q.3 State the effects of force on a body.

Ans. :

Force acting on a body has the following two effects on the body.

i) It can produce motion-either translation or rotation, and

ii) It can produce deformation.

Q.4 State Newton's first law of motion.

Ans. :

Every body tries to be in its state of rest or of uniform motion along a straight line unless it is acted upon by an external unbalanced force.

Q.5  State Newton's second law of motion.

Ans. : 

The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force.

Q.6  State Newton's third law of motion.

Ans. : 

Every action has an equal and opposite reaction.

Q.7 State Newton's law of gravitation.

Ans. : 

Every body in the universe attracts every other body with a force whose magnitude is directly proportional to the product of the two masses and inversely proportional to square of the distance between them.

Q.8 State law of parallelogram of vectors.

Ans. : 

If two vectors are represented in magnitude and direction by two adjacent sides of a parallelogram, their resultant is represented in magnitude and direction by the diagonal of the parallelogram drawn from the common point.

Q.9 State the principle of transmissibility of forces with simple sketch.

Ans. : 

According to principle of transmissibility of force, the force can be transmitted from one point to another on its line of action without causing any change in the motion of the object. i.e., force F can be transmitted from A to B as shown in Fig. 1.12.1.

Q.10 Define Body forces giving example.

Ans.

Forces exerted by one body on another without physical contact are known as body forces. For example gravitational force.

Q.11 Define unit vector.

Ans. :

A vector having magnitude one unit is known as a unit vector.

Q.12 Give geometrical interpretation of dot product of two vectors.

Ans. :

Q.13 Give geometrical interpretation of cross product of two vectors.

Ans. : 

i) If represent two adjacent sides of a parallelogram, the area of parallelogram is

ii) If represent two sides of a triangle, then is twice the area of that triangle.

Q.14

Ans. : 

Q.17 If A(x1, y1, z1) and B(x2, y2, z2) are two points in space, write the vector

Ans. : 

Q.18 Iƒ A(x1, y1, z1) and B(x2, y2, z2) are two points in space write the unit vector directed from A to B.

Ans. : 

Q.19 If θx, θy and θz are the angles made by a vector with X, Y and Z axes respectively, write the equation relating these angles.

Ans.: 

cos2θx + cos2θy + cos2θz = 1

Q.20 Define the following terms:

(a) Coplanar forces (b) Concurrent forces.

Ans. :

 If all forces act in one plane, they are known as coplanar forces.

If lines of action of all forces intersect at a single point, the forces are known as concurrent forces.

Q.21 Differentiate between collinear and concurrent forces.

Ans. 

Collinear forces act along the same line whereas concurrent forces have lines of action intersecting at one point.

Q.22 Find the length of the line joining the origin with the point (2, 1, − 2).

Ans. 

Length of line is given by,

Q.23 Two forces 30 N and 40 N act at a point 'O'. The included ange between them is 60°. Find the magnitde and the direction of the resultant.

Ans. 

Q.24 Find the resultant and direction of Force

Ans. 

Q.25 State the polygon law of forces.

Ans. 

If two vectors are represented in magnitude and direction by two sides of a triangle taken in order, their resultant is represented in magnitude and direction by the third side of the triangle drawn from starting point of first vector to end point of second vector.

Q.26 Two forces of 400 N and 600 N act at an angle 60° to each other. Determine the resultant in magnitude and direction.

Ans. 

Let P = 400 N, Q = 600 N, α = 60°

By parallelogram law,

Q.27 Give two practical applications, from where the concept of cross product envolved.

Ans.:

1) Opening and closing of a tap

2) Installation of solar panel to produce electric power

3) When the door is opened and closed.

4) Put a screw in or out

Q.28 Name the principle that is applicable for the conditions represente Fig. 1.12.4.

Ans.:

Principle of transmissibility of force is applicable for the conditions represented in Fig. 1.12.4.