How did scientists discover the earth had a liquid outer core and solid inner core?

Me to solve all the questions on the sheet attached

1. a camcorder has a power rating of 19 watts. if the output voltage from its battery is 7 volts, what current does it use?answer units 2. a 1.5m wire carries a 6 a current when a potential difference of 57 v is applied. what is the resistance of the wire? your

Acar travels in reverse. it covers 150 meters in 12 seconds what is the velocity of the car what is the speed of the car