A rock is dropped from a cliff. Approximately how long does it take to fall 45m if the acceleration due to gravity is 9.8 m/sec2

Astudent creates a model of a closed ecosystem by filling a glass tank half full with water, then adding 10 snails and two small aquatic plants. the next day, all the snails are dead. what is the most likely cause of their death?

A100 kg running back runs at 5m/s into a stationary linebacker. it takes 0.5 for the running back to be completely stopped

Yvette hangs a 2.4kg bird feeder in the middle of a rope tied between two trees. the feeder creates a tension of 480 n in each side of the the rope.