A phone is knocked off a table 800cm of the ground. If the phone is 650g a) what is the gravational potential of the phone? b)what speed will the phone hit the floor at? c)How long will it take for the phone to hit the floor?

UNITS - SI UNITS: 800cm --> 0.8m  0.65kg

a) Ep= mg(change) height

Ep=0.65kg * 9.81m/s² * 0.80m

Ep=5.10 Joules (J)

b) Gravational Potential = Kinetic energy

Ek = 1/2 mv² 

v=Sqrt(Ep/0.5m)

v=sqrt(5.10/0.5*0.65)

v=3.96m/s

c) v=u+ at

t=(v-u)/a

v=3.96m/s u=0m.s  a=9.81m/s²

t=3.96/9.81

t=0.40s