Physics

A balloon of total mass 1000 kg floats motionless in the air. If 100 kg of sand ballast are thrown overboard the baloon, with what acceleration does the balloon start to rise and what will be its velocity after 9 seconds?
Assume g = 10m/s^2

If 100kg is thrown overboard, Acceleration is given by
100g = (1000-100)a
a = g/9 = 1.11 m/s^2

After 9s, velocity is given by
v= at = 1.11x9 = 10m/s

Two objects of masses 2 kg and 3 kg are suspended by taut string passing over a frictionless pulley. Determine the acceleration of the two objects and the tension in the string when the system is released.
Assume g = 10m/s^2
Let acceleration = a and Tension = T
2a = T - 2g
3a = 3g - T
5a = g
a = g/5 = 2 m/s^2
T = 2(a+g) = 2 (2+10) = 24N