Several experiments in the 1800s demonstrated that the tips of plants are responsible for detecting light, which causes the stem of the plant to elongate and bend towards the light.

Which of these phrases are accurate about the experimental design and its validity?

The experiment should be repeatable by the same researcher.
The experiment should be replicated by different researchers.
A control plant with no light or top light would likely show no bending.
All species of plants behave the same way.
The light levels should increase during the experiment as the plant grows.

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12

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