A spring gun (k = 500 N/m, compressed 5 cm) fires a 25 g ball vertically. Max height reached: <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 180 280" style="max-width:180px;margin:0.5em auto;display:block;"> <title>Spring gun firing ball vertically</title> <rect width="180" height="280" fill="#faf9f5" rx="6"/> <defs><marker id="ah-q77-03" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"><polygon points="0 0, 8 3, 0 6" fill="#c6613f"/></marker></defs> <!-- Tube/barrel --> <rect x="70" y="140" width="40" height="100" fill="none" stroke="#14140f" stroke-width="1.5" rx="2"/> <!-- Spring inside barrel --> <path d="M90,238 L90,230 L78,222 L102,214 L78,206 L102,198 L78,190 L102,182 L90,174 L90,168" fill="none" stroke="#14140f" stroke-width="1.5"/> <!-- Ball on spring --> <circle cx="90" cy="155" r="12" fill="#f0e8e0" stroke="#14140f" stroke-width="1.5"/> <text x="90" y="159" text-anchor="middle" font-size="8" font-family="sans-serif" fill="#14140f">25g</text> <!-- Compression arrow --> <line x1="55" y1="168" x2="55" y2="238" stroke="#c6613f" stroke-width="1"/> <line x1="51" y1="168" x2="59" y2="168" stroke="#c6613f" stroke-width="1"/> <line x1="51" y1="238" x2="59" y2="238" stroke="#c6613f" stroke-width="1"/> <text x="45" y="205" text-anchor="end" font-size="8" font-family="sans-serif" fill="#c6613f">5 cm</text> <!-- Velocity arrow upward --> <line x1="90" y1="140" x2="90" y2="100" stroke="#c6613f" stroke-width="2" marker-end="url(#ah-q77-03)"/> <!-- Ball at top (ghost) --> <circle cx="90" cy="30" r="12" fill="none" stroke="#c6613f" stroke-width="1.5" stroke-dasharray="4,3"/> <!-- Dashed path --> <line x1="90" y1="98" x2="90" y2="44" stroke="#14140f" stroke-width="1" stroke-dasharray="4,3"/> <!-- Height label --> <line x1="130" y1="30" x2="130" y2="140" stroke="#788c5d" stroke-width="1"/> <line x1="126" y1="30" x2="134" y2="30" stroke="#788c5d" stroke-width="1"/> <line x1="126" y1="140" x2="134" y2="140" stroke="#788c5d" stroke-width="1"/> <text x="142" y="90" font-size="9" font-family="sans-serif" fill="#788c5d">h=?</text> <!-- Ground --> <line x1="40" y1="252" x2="140" y2="252" stroke="#14140f" stroke-width="1.5"/> <text x="90" y="268" text-anchor="middle" font-size="8" font-family="sans-serif" fill="#14140f">k = 500 N/m</text> </svg>

A 10 kW engine pulls a train at constant 36 km/h. Total friction force:

Two objects (2 kg at 3 m/s and 3 kg at 2 m/s) move in same direction, collide elastically. Speed of 2 kg after collision:

A car of mass 1000 kg accelerates from rest. Engine power = 20 kW. Time to reach 20 m/s (no friction):

A body of mass 4 kg moving at 3 m/s has a force applied that increases its speed to 5 m/s. Work done by the force: