07. what is the velocity of a 500kg elevator that has 4000j of energy?
1) givens & unknown:
2) formula:
3) sub & solve:

v = 4 m/s

Explanation:

Given data:

Mass of elevator = 500 kg

Energy = 4000 j

Velocity = ?

Solution:

1/2 mv²  =  4000 j

1/2 (500 kg)v²  =  4000 j

v²  =  4000 j×2 / 500 kg

v²  =  4000 kg. m²/s² ×2 /  500 kg

v²  = 8000 kg. m²/s² /  500 kg

j =  kg. m²/s²

v²  = 16 m²/s²

v = 4 m/s

hey there!

mass = 6.75 g

volume =   9 cm³

therefore:

d = mass / volume

d   = 6.75 / 9

d = 0.7 g/cm³

answer b