Answer:
1/2mv^2 a(7.5 b(15 kg c(60 kg d(120 kg. nevermind i found the answer its (15 kg) because to solve for m its m= K2/v squared.
Explanation:
Answer:9.75 m/s
Explanation:
Given
Length of ladder 
Foot the ladder is moving away with speed of 
From diagram
------1
at 


Now differentiating equation 1 w.r.t time




negative indicates distance is decreasing with time
There are 3 significant figures, if that answers the question.