Energy lost to friction on a ramp
A 2 kg block starts from rest at the top of a ramp 5 m high and reaches the bottom at 8 m/s. Using g = 10 m/s², how much energy was lost to friction?
Answer B: explanation for every choice
A
This leaves out the mass: gh − ½v² = 50 − 32 = 18.
B
Correct. Energy lost = mgh − ½mv² = 100 − 64 = 36 J.
C
64 J is the kinetic energy at the bottom.
D
100 J is the initial potential energy.
TakeawayEnergy lost to friction = starting mechanical energy − final mechanical energy.
Equation usedKinetic and gravitational potential energy
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