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A particle acted upon by constant forces `4hati +hatj- 4 hatk` and `3hati + hatj - hatk` is displacment from the point `hati+ 2hatj+ hatk` to point `5hati + 4hatj +hatk`.Total work done by the forces in SI unit is :A. 20B. 40C. 50D. 30 |
Answer» Correct Answer - B Here, `vecF_1=4hati+hatj-3hatk,vecF_2=3hati+hatj-hatk` `vecr_1=hati+2hatj+3hatk, vecr_2=5hati+4hatj+hatk` Displacement , `vecr=vecr_2-vecr_1` `=(5hati+4hatj+hatk)-(hati+2hatj+3hatk)=4hati+2hatj-2hatk` Work done by the forces, `W=[vecF_1+vecF_2].vecr` `=[(4hati+hatj-3hatk)+(3hati+hatj-hatk)].(4hati+2hatj-2hatk)` `=(7hati+2hatj-4hatk).(4hati+2hatj-2hatk)=28+4+8=40 J` |
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