How many joules of PE does a 12 kg rock have after falling from a 76 m cliff and reaches 7 m/s?
+33615 "How many joules of PE does a 12 kg rock have after falling from a 76 m cliff and reaches 7 m/s?"
E = PE + KE E is total energy, PE is potential energy, KE is kinetic energy.
Top of cliff: E = 12*9.8*76 + 0 joules
E stays constant so when velocity is 7 m/s
12*9.8*76 = PE + (1/2)*12*7^2
PE = 12*9.8*76 - (1/2)*12*7^2 or PE ≈ 9314 joules
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