PLEASE HELP ASAP

How much force is need
to accelerate a 50 kg
object 20 m/s2?

If a balloon is taken outside on a very cold day, what will occur?

A2000 kg car is rounding a curve of radius 200 m on a level road. the maximum frictional force the road can exert on the tires of the car is 4000 n. what is the highest speed at which the car can round the curve?

The voltage applied across a given parallel-plate capacitor is doubled. how is the energy stored in the capacitor affected?