Me! i have to slove this. i have to find x , y and z

When you drop a pebble from height a it reaches the ground with speed v if there is no air resistance. from what height should you drop it so it will reach the ground with three times the speed? (a) 9m (b) 3m (c) 6m (d) 18m

What is the type of the reaction below? bacl2 + h2so4 → 2 hci + baso4 double replacement synthesis single replacement decomposition

Calculate the mass of an object that has a momentum of 100kg x m/sec and velocity of 4 m/sec