A child's sled has rails that slide with little friction across the snow. Logan has an old wooden sled with heavy iron rails that has a mass of \(10 \mathrm{~kg}\)-quite a bit for a \(30 \mathrm{~kg}\) child! Logan runs at \(4.0 \mathrm{~m} / \mathrm{s}\) and leaps onto the stationary sled and holds on tight as it slides forward. The impact time with the sled is \(0.25 \mathrm{~s}\).

a. Immediately after Logan jumps on the sled, how fast is it moving?

b. What was the force on the sled during the impact?

c. How much energy was "lost" in the impact? Where did this energy go?