Why are some planets made of frozen gases and others solid?

What are the pros and cons of quadrat sampling?

After a group of researchers conducts a new experiment that has never been conducted before, what is the best way for other scientists to make sure that the data is real

1. you serve a volleyball with a mass of 2.1 kg. the ball leaves your hand with a speed of 30 m/s. the ball has energy. calculate it. 2. a baby carriage is sitting at the top of a hill that is 21 m high. the carriage with the baby weighs 12 n. the carriage has energy. calculate it. 3. a car is traveling with a velocity of 40 m/s and has a mass of 1120 kg. the car has . calculate it.