cm, how much energy is converted into thermal energy in the bag?
My answer: Given: m(sandbag) = 24.0 kg m(bullet) = 15.0 g = 0.015 kg v = 840 m/s d = 80.0 cm = 0.8 m Required: E(thermal) Analysis: F = mg Ep = W = Force x displacement Ek = 1/2mv^2 E(thermal) = Ep + Ek Solution: F = (m(sandbag)+ m(bullet))g F = (24.0 kg + 0.015 kg)9.8 m/s^2 F = 24.015 kg x 9.8 m/s^2 F = 235.3 J Ep = 235.3 J x 0.8 m Ep = 188.24 J Ek = 1/2(0.015 kg)(840 m/s)^2 Ek = 1/2(0.015 kg)(705600 m/s) Ek = 5292 Et = 188.24 J + 5292 J = 5480.24 J Paraphrase: The amount of energy converted into thermal energy in the bag is 5.5 x 10^3 J. ANSWER: You’ve got some really wrong units here, force is not in Joules (for example). Just consider this. You know how much energy went into the system in the collision, it was all in the bullet. And you were right to add the masses and look at the energy that went into pushing the sand bag + bullet up 80.0 cm. But you’ll find that answer is slightly less than the initial energy, because during the collision some energy is converted into thermal ene
