A plank AB 3.0m long weighs 20kg and with it's centre of gravity 2.0m from the end A. it rests on two supports at C and D. i) compute the values of the reaction forces R1 and R2 at C and D . ii) how far from D and in which side of it must a mass of 24kg be placed on the plane so as to make the reaction equal? what are their values ? iii) without this 24kg ,what vertical force applied at B will just lift the plank clear of D ? what is then the reaction at C

First, launch the video below. you will be asked to use your knowledge of physics to predict the outcome of an experiment. then, close the video window and answer the question at right. you can watch the video again at any point. part a as in the video, we apply a charge +q to the half-shell that carries the electroscope. this time, we also apply a charge –q to the other half-shell. when we bring the two halves together, we observe that the electroscope discharges, just as in the video. what does the electroscope needle do when you separate the two half-shells again? view available hint(s) as in the video, we apply a charge + to the half-shell that carries the electroscope. this time, we also apply a charge – to the other half-shell. when we bring the two halves together, we observe that the electroscope discharges, just as in the video. what does the electroscope needle do when you separate the two half-shells again? it deflects more than it did at the end of the video. it deflects the same amount as at end of the video. it does not deflect at all. it deflects less than it did at the end of the video. submit

*drag each tile to the correct location in the sequence* the table shows chronological events in the life of our sun, a medium-sized star. place the missing events into the correct rows of the table.

Aa a of 22 m/s at an of 36.9 .be . a. b. c. (3)x y of? (3)go? (4) () it to to ?