Page 72 - Mathematics Class - X

INFERENCE
We have found the height of a building using clinometer.

EXTENDED TASK
1. Find the height of a tree by using a clinometer.
2. Find the height of a pole in your locality.

APPLICATION

1. A clinometer can be used to measure an angle of elevation and an angle of depression.
2. It is also used to measure the height of distant objects, where it is difficult to measure the height directly.

Viva-Voce

1. What is clinometer?

Ans. An instrument used to measure the height of an object.
2. When an observer moves towards the building, does angle of elevation increases or decreases?

Ans. Angle of elevation increases.
3. How would you define the angle of depression?
Ans. Angle of depression of an object is the angle formed by the line of sight with the horizontal, when it is below
the horizontal level, i.e. the case when we lower our head to look at the object.

4. In the figure, find PR in terms of (i) x, (ii) y.

Ans. In ∆PQR, we have:

QR
(i) sin 60° = y
PR

3 x 2x 2 3x
∴ = ⇒ PR = = x
2 PR 3 3
PQ
(ii) sin 30° =
PR

1 y
∴ = ⇒ PR = 2y
2 PR
5. Can we measure height of an object with the help of clinometer whose position is not vertical with base?

Ans. This is possible, only if we can adjust the clinometer in such a way that angle between the base line of
clinometer and object is 90º.

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