A plank AB 3.0 m long weighing 20 kg and with its centre of gravity 2.0 m from the end A
carries a load of mass 10 kg at the end 4. It
rests on two supports at C and D as shown in
RA
B В
4
50 cm
50 cm
(1) Compute the values of the reaction
forces R; and R, at Cand D.
How far from D. and on which side of it,
must a mass of 24 kg be placed on the
plank so as to make the reactions equal?
What are their values?
(m) Without this 24 kg, what vertical force
applied at B will just lift the plank clear 30
of D? What is then the reaction at C?​

Laboratory experiments, observational field studies, and model-building are all examples of different forms of scientific investigations.  in what way do laboratory experiments primarily differ from other forms of scientific investigations?   a.  a laboratory experiment is the only accepted form of investigation within the scientific community.  b.  studies about how things behave in nature or studies involving very large objects are best answered through laboratory experiments.  c.  laboratory experiments involve the identification and control of variables.  d.  data can only be generated through laboratory experiments, not other forms of investigation.

Unpolarized light of intensity i_0=750w/m^2 is incident upon two polarizers. after passing through both polarizers the intensity is i_2=280w/m^2. (a) what is the intensity of the light after it passes through the first polarizer in w/m^2? (b) write an equation for the angle between the polarizers in terms of the initial (i_0) and final (i_2) intensities. (c) find the angle between the polarizers in degrees.

What are atoms of the same element with varying number of neutrons