- #1
Dusty912
- 149
- 1
Homework Statement
(Picture attached)
Question 1: The system starts at rest. Block a accelerates towards the bottom the the rod. Find the velocity of the block when it is at the bottom of the rod using the "vector method". So this was my midterm question today. I knew how to figure out how fast it was going using work emery method and found the velocity to be 3.16 meters per second which I know is the right answer. But, I cannot find anything about a "vector method" could someone help me understand what this is indicating?
Question 2: find the tension in the string. I believe I found this to be about 264.9 by finding out how fast block A is accelerating and then applying the dynamic equilibrium force equation and solving for T
Homework Equations
L=2Xa +Xb (the length of the string that is changing with time)
F=ma (in y-direc)
for block A
2T-mag=m*a
The Attempt at a Solution
question 1:
applying a time derivative to L yields
0=2x'a+x'b
and taking another:
0=2x''a+x''b
Ill stop here for question 1 because I am just wondering what vector method is indicating to do. The correct velocity is 3.16m/s (I know this is correct)
question 2:
if block a moves .6 meters from initial velocity zero to velocity 3.16 then it is accelerating at 8.32 m/s2 by applying the kinematics equation. by subbing in my values to :
2T-mag-500=m*a
I got T=264.9NI also applied the dynamic equilibrium expression to block B and got the same result
is this correct?
for block B T-mg=ma
acceleration of B is 16.64
subbing in the values gets 264.9 again.
This seems fairly straightforward for question 2 but a lot of people I talked to had different answers.
by the way for the first question, I know you all have a policy that you do not give solutions, but I have already taken the exam and am just wondering what I should have done instead. The second question just needs to be reviewed. Thanks ahead of time. you all rock!