An air puck of mass m1 = 0.28 kg is tied to a string and allowed to revolve in a circle of radius? PHYSICS

An air puck of mass m1 = 0.28 kg is tied to a string and allowed to revolve in a circle of radius R = 1.4 m on a frictionless horizontal table. The other end of the string passes through a hole in the center of the table, and a mass of m2 = 1.0 kg is tied to it (see the figure below). The suspended mass remains in equilibrium while the puck on the tabletop revolves.

http://www.webassign.net/sercp9/7-p-027.…

(a) What is the tension in the string?
____ N

(b) What is the horizontal force acting on the puck?
____ N

(c) What is the speed of the puck?
____ m/s

So I keep getting the tension wrong and I don't know what I'm doing wrong. I did T = 0.28v^2/1.4=1 x 9.81 and just no. Please work it through with me and your answer so I can compare. For part B is it talking about the radius? Thanks in advance.

You have the correct set up.
(a) Since the hanging mass is motionless the tension in string equals the force of gravity on mass m2, therefore T = 9.8 N
(b) The horizontal force on the puck (which is the centripetal force) is the same as the tension.
F(horizontal) = 9.8 N
(c) mv^2 / r = F(centripetal) ===> (0.28)(v^2) / (1.4) = 9.8 ===> v = 7 m/s

a) The m2 is not moving, therefore, the force acting on m2 must be balance.
T = tension pulling up
force acting down on m2 = m2 g
T = m2 g = 1*9.8= 9.8 N
b) Horizontal force acting on the puck is the same as the tension.
c) Since the puck is moving in a circle, the centripetal force is the same as the tension
m2 v^2/r = T
=> v = (T r /m2)^(1/2) = 7.0 m/s

a) 9.8N.
b) 9.8N.
c) V = sqrt.(fr/m), = sqrt.(9.8x1.4)/0.28, = 7m/sec.