In #16 you found the acceleration of the masses. Mass 1 is accelerating upwards and masses 2 and 3 are accelerating downwards.
To find the tension in the string between masses 1 and 2 (question #17) you can look at the forces acting on mass 1. There is the force due to gravity (Fg = m1*g) which is downward. There is the tension (call it T) between masses 1 and 2 which is what you are looking for. This is pulling upward on mass 1, so it is an upward force.
Now use Newton's 2nd law for the forces on mass 1. If you pick upward as positive (because the acceleration is upward so the right hand side of the equation will be positive) you get: ∑F=T-Fg=m1*a. You can plug in Fg=m1*g and then solve for T. That's the answer for #17.
You do basically the same thing to find #18. Look at the forces acting on mass #3, and remember that the acceleration of mass #3 is downward.
4 comments:
In #16 you found the acceleration of the masses. Mass 1 is accelerating upwards and masses 2 and 3 are accelerating downwards.
To find the tension in the string between masses 1 and 2 (question #17) you can look at the forces acting on mass 1. There is the force due to gravity (Fg = m1*g) which is downward. There is the tension (call it T) between masses 1 and 2 which is what you are looking for. This is pulling upward on mass 1, so it is an upward force.
Now use Newton's 2nd law for the forces on mass 1. If you pick upward as positive (because the acceleration is upward so the right hand side of the equation will be positive) you get: ∑F=T-Fg=m1*a. You can plug in Fg=m1*g and then solve for T. That's the answer for #17.
You do basically the same thing to find #18. Look at the forces acting on mass #3, and remember that the acceleration of mass #3 is downward.
Good luck.
Thank you!
I am still really confused on how to find number 18. If you are still there, can you help me? I already tried it 5 times.
Never mind.
Post a Comment