No, if three vectors do not lie in a plane, they cannot give zero resultant.

Explanation:

Let A, B and C be three vectors. If they give zero resultant, then

     A+B+C=0

or, A= -(B+C)

Hence, they will produce zero resultant, if A is equal to negative of vector (B+C). The vector (B+C) lies in the plane of B and C. Hence, A will be equal to negative of (B+C) if A, B and C all lie in a plane.

1.ans:  No the tension in the string of a simple pendulum is not constant throughout the motion                                     

v is velocity of the bob and theta is the angle made by the string with vertical axis.

as v and θ both are variable T is also variable.

T is maximum at mean position as at mean position v is max and the angle is minimum.

2.ans: If the amplitude of the simple...

1) That old man is Aksionov.

2) The speaker is asking about the truth of digging an escape hole .

3) The speaker means the prison's wall.