Two particles P P\,P and Q Q\,Q of mass 4 kg and 6 kg respectively are connected by a light inextensible string. Particle P P\,P is placed on a rough plane inclined at an angle θ \theta\,θ to the horizontal, where tanθ=4/3\tan \theta = 4/3tanθ=4/3. The string passes over a smooth fixed pulley at the top of the plane, and Q Q\,Q hangs freely. The part of the string between P P\,P and the pulley is parallel to the line of greatest slope of the plane. The coefficient of friction between P P\,P and the plane is 0.5. The system is released from rest with P P\,P moving up the plane.
Calculate the tension in the string during the motion.
When Q Q\,Q hits the ground, P P\,P continues to move up the plane until it momentarily comes to rest. Determine, with justification, whether P P\,P will remain at rest or slide back down the plane.
Suggest two refinements to the model that would make it more realistic.
139 exam-style questions on OCR A Level Maths 3.3 Forces and Newton's Laws, covering 3.3.1 Concept and vector nature of a force, 3.3.2 Newton's first law, 3.3.3 Newton's second law in a straight line, 3.3.4 Newton's second law with vectors (A-level only), 3.3.5 Newton's second law with resolved forces (A-level only), 3.3.6 Weight, 3.3.7 Gravitational acceleration, 3.3.8 Newton's third law, 3.3.9 Normal reaction force, 3.3.10 Smooth contact model, 3.3.11 Equilibrium with connected particles and pulleys, 3.3.12 Newton's third law with resolved forces (A-level only), 3.3.13 Equilibrium by resolving (A-level only), 3.3.14 Equilibrium of forces in two dimensions using vectors (A-level only), 3.3.15 Resolving forces for advanced problems (A-level only), 3.3.16 Resultant forces and components (A-level only), 3.3.17 Dynamics of a particle in a plane (A-level only), 3.3.18 Concept of a frictional force (A-level only), 3.3.19 Contact force components (A-level only), 3.3.20 Coefficient of friction (A-level only), 3.3.21 Static and limiting equilibrium on a rough surface (A-level only), 3.3.22 Motion of a body on a rough surface (A-level only), and 3.3 Forces and Newton's Laws. Each one has a worked solution and a mark scheme showing where the marks go.