Answer:
Rate of change of area will be 
Explanation:
We have given rate of change of radius 
Radius of the circular plate r = 52 cm
Area is given by 
So 
Puting the value of r and 

So rate of change of area will be 
A would be the correct answer. Its the only one to make sense since you are trying to solve the conflict!
Answer:
Given, Apparent weight(W₂)=4.2N
Weight of liquid displaced (u)=2.5N
Let weight of body in air = W₁
Solution,
U=W₁-W₂
W₁=4.2=2.5=6.7N
∴Weight of body in air is 6.7N
Answer:
80m<em>/</em><em>s</em>
Explanation:
Final velocity is given by
v=u+at
when a motorcyclist starts from rest, initial velocity (u) =0
therefore
v=0+4*20
v=80m/s
that's the answer