Question

Example 10. Two constant forces P = 2i-5j+6k
and Q=- i+2 j-k are acting on a particle. If par-
ticle is displaced from A to B and position vectors
of A and B are 4i-3 j-2k and 6i+ j-3k respectively then calculate the work done.​

Answer 1

Answer:

15 units

Step by step Explanation:

If R is the resultant of two forces P and Q.

then,

 R=P+Q=i−3j+5k. ...(simple vector addition done here)

Also the displacement of the particle = AB

Or, AB= (6i+j−3k)−(4i−3j−2k)

=2i+4j−k.

Hence, required work done = R.AB

= (i−3j+5k).(2i+4j−k) ...(dot product of vectors)

 = 2−12−5

= −15 units

[ Note: above AB means,AB is vector all the time in answer, vector sign is not present in my keyboard,sorry! ]