Question

27. A force of 6i +121 +8k produces a displacement of
21 +81 +2k. Find the work done.

28. Find the work done by a force F = 3i+5j + k which produces a
displacement of S=21 +1 +4k.

29. If Ā=i-1 +2k and B = 21 +1+k are two vectors, then find
the angle between them.
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Answer 1

Explanation:

.A battery of e.m.f 15 V and internal resistance 3 ohm is connected to two resistors of resistances 3 ohm and 6 ohm in series. The p.d between the terminals of the battery is

Answer 2

Explanation:

27. Force acting on the particle, F=(2i+3j+4k)\ NF=(2i+3j+4k) N

Displacement of the particle, d=(3i+4j+5k)\ md=(3i+4j+5k) m

Time, t = 4 s

To find,

The power used by the body.

Solution,

The work done per unit time by an object is called power used by it. it is given by :

P=\dfrac{W}{t}P=

t

W

W is work done,

W=F{\cdot} dW=F⋅d

W=(2i+3j+4k){\cdot} (3i+4j+5k)W=(2i+3j+4k)⋅(3i+4j+5k)

W=6+12+20=38\ JW=6+12+20=38 J

So,

P=\dfrac{38\ J}{4\ s}P=

4 s

38 J

P = 9.5 watts

So, the power used by the body is 9.5 watts. Hence, this is the required solution.

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