Moderate -0.8 This is a straightforward application of the work-energy principle with a single step: calculate the change in kinetic energy and equate it to work done by the constant resistive force over the given distance. It requires only standard formula recall (KE = ½mv², Work = Fd) with no problem-solving insight or multiple stages, making it easier than average.
2 A bullet of mass 9 grams passes horizontally through a fixed vertical board of thickness 3 cm . The speed of the bullet is reduced from \(250 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) to \(150 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) as it passes through the board. The board exerts a constant resistive force on the bullet. Calculate the magnitude of this resistive force.
2 A bullet of mass 9 grams passes horizontally through a fixed vertical board of thickness 3 cm . The speed of the bullet is reduced from $250 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ to $150 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ as it passes through the board. The board exerts a constant resistive force on the bullet. Calculate the magnitude of this resistive force.
\hfill \mbox{\textit{OCR M2 2008 Q2 [4]}}