Question

A body is executing the SHM. What fraction of its total energy will be kinetic energy when it
displacement from the mean position is half of its amplitude?
(GRW 2013
3
(A
(B)
(C)
(D)
2
4
The P.E. stored by a mass spring system at an extension of 2cm is 10J. The P.E. stored by the sam​

Answer 1

Question 1:

The angles between North and West and South and East are

(a) complementary (b) supplementary

(c) both are acute (d) both are obtuse

Solution :

ncert-exemplar-problems-class-7-maths-lines-and-angles-1s

From the above figure, it is clear that the angle between North and West is 90° and

South and East is 90°.

∴ Sum of these two angles = 90° + 90° = 180°

Hence, the two angles are supplementary, as their sum is 180°.

Question 2:

Angles between South and West and South and East are

(a) vertically opposite angles (b) complementary angles

(c) making a linear pair (d) adjacent but not supplementary

Solution :

ncert-exemplar-problems-class-7-maths-lines-and-angles-2s

From the above figure, we can say that angle between South and West is 90° and

angle between South and East is 90°. So, their sum is 180°.

Hence, both angles make a linear pair.

Question 3:

In the given figure, PQ is a mirror, AB is the incident ray and BC is the reflected ray. If ∠ABC = 46°, then ∠ABP is equal to

ncert-exemplar-problems-class-7-maths-lines-and-angles-3

Solution :

(b) We know that, the angle of incidence is always equal to the angle of reflection.

ncert-exemplar-problems-class-7-maths-lines-and-angles-3s

Question 4:

If the complement of an angle is 79°, then the angle will be of

(a) 1° (b) 11°

(c) 79° (d) 101°

Solution :

(b) Let the angle be x°. Then, the complement of