Question

Arrange the examples in order, starting with the object that has the least amount of energy. In each case, assume there’s no friction. Use g = 9.8 m/s2, PE = m × g × h, and . Tiles a book with a mass of 0.75 kilograms resting on a shelf at a height of 1.5 metersa brick with a mass of 2.5 kilograms falling with a velocity of 10 meters/second when it’s 4 meters above grounda ball with a mass of 0.25 kilograms rolling on flat ground with a velocity of 10 meters/seconda stone with a mass of 0.7 kilograms being held still at a height of 7 meters

Answer 1

First example: book, m= 0.75 kg, h=1.5 m, g= 9.8 m/s², it has only potential energy Ep,

Ep=m*g*h=0.75*9.8*1.5=11.025 J

Second example: brick, m=2.5 kg, v=10 m/s, h=4 m, it has potential energy Ep and kinetic energy Ek,

E=Ep+Ek=m*g*h + (1/2)*m*v²=98 J + 125 J= 223 J

Third example: ball, m=0.25 kg, v= 10 m/s, it has only kinetic energy Ek

Ek=(1/2)*m*v²=12.5 J.

Fourth example: stone, m=0.7 kg, h=7 m, it has only potential energy Ep,

Ep=m*g*h=0.7*9.8*7=48.02 J

The order of examples starting with the lowest energy:

1. book, 2. ball, 3. stone, 4. brick