A student is investigating the force and motion of a model rocket car powered by a small gas thruster.
First, the thruster is fired while a force sensor holds the model stationary. The sensor measures a thrust force of 0.12 N0.12\text{ N}0.12 N acting on the model.
Next, the force sensor is disconnected and the model is released from rest, accelerating at 0.040 m/s20.040\text{ m/s}^20.040 m/s2 along a track.
The rear of the model passes through a pair of photogates. The gates are 15 mm15\text{ mm}15 mm apart, and the time taken to pass between them is measured to be 0.050 s0.050\text{ s}0.050 s. The student uses a stopwatch to measure the total time from the release of the model until the photogates are reached. Calculate this time.
Calculate the mass of the model rocket car (including the gas thruster canister).
The student repeats the experiment with the same thrust force, but with the thruster canister nearly empty. State and explain how the acceleration compares to that of the first run.
245 exam-style questions on CIE IGCSE Physics 1.5 Forces, covering 1.5.1a Forces, resultant force and motion, 1.5.1b Load–extension graphs and the spring constant, 1.5.1c Friction and drag, 1.5.1d Force, mass and acceleration, 1.5.1e Motion in a circular path, 1.5.2a Moment of a force, 1.5.2b Principle of moments and equilibrium, and 1.5.3 Centre of gravity and stability. Each one has a worked solution and a mark scheme showing where the marks go.