PLEASE help - more M1 problems,

Its me again, just realise i had more work set, and as our teacher is worse than useless, i would really appreciate any help you can give.

I really have tried my hardest, and i've managed to do some of the questions, but here are those that i can't do.

2. A boy of mass of 60kg is standing in a lift that has an upward acceleration of magnitude 0.5ms-2. Describe the forces acting on the boy, and find their magnitudes.

4. A balloon of total mass 420kg is descending with a constant acceleration of 0.4ms-2. Find the upthrust acting on the balloon. When the balloon is moving at 1.5ms-1, enough ballast is released for the balloon to fall with a deceleration of 0.2ms-2. Calculate
a) how much ballast was released
b) the time for which the balloon continues to fall before it begins to rise.

7. A stone of mass m is released from rest on the surface of a tank of water of depth d. During the motion, the water exerts a constant resisting force of magnitude r. The stone takes t seconds to reach the bottom of the tank. Show that r=m(g- 2d/t squared)

8. An acrobat of mass m slides down a vertical rope of height h. For the first three quaters of her decent she grips the rope with her hands and legs as to produce a frictional force equal to five ninths of her weight. She then tightens her grip so that she comes to rest at the bottom of the rope. Sketch a (t,v) graph to illustrate her decent, and find the frictional force she must produce in the last quater. If the rope is 30 meters high, calculate
a) her greatest spees
b) the time she takes to decend.

9. In a lab experiment the motion of a steel ball-bearing falling vertically in a tank containing liquid is observed.
a)state why the acceleration of the ball bearing is less than g
b)The ball bearing of mass 0.15kg is released from rest in the liquid, and after 0.60 seconds it has fallen a distance of 1.53m. Assuming that the acceleration has a constant value of a ms-2, find a and the magnitude of the force resisting the motion.

10. A lift travels vertically upwards from rest at floor a to rest at floor b, which is 20m above a, in 3 stages, as follows. At first the lift accelerates from rest at a at 2ms-2 for 2s. It then travels at a constant speed and finally it decelerates uniformly, coming to rest at b after a total time of 6 1/2s. Sketch the (t,v) graph for this motion, and find the magnitude of the constant deceleration.

The mass of the lift and its contents is 500kg. Find the tension in the lift cable during the stage of the motion when the lift is accelerating upwards.

If you can help with any i would appreciate sooooooooo much. Thankyou.