Hey, can someone me with this? i'll all useful answers

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

While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. her friend, a hockey player, then shoots a hockey puck at each shoe. the first puck immediately comes to rest after it collides with the left shoe. the second puck rebounds after it collides with the right shoe. if each hockey puck has the same incoming speed, which shoe has greater speed after the collision? the right shoe. both shoes have the same speed. the left shoe.

Ahockey player of mass 82 kg is traveling north with a velocity of 4.1 meters per second he collides with the 76 kg player traveling east at 3.4 meters per second if the two players locked together momentarily in what direction will they be going immediately after the collision how fast will they be moving