Laws of Motion and Momentum 0.0 / 5 ? PhysicsForcesMomentum and ImpulseMotionA2/A-levelOCR Created by: CPev3Created on: 16-06-20 11:31 Newton's first law of motion An object will remain at rest or continue to move with constant velocity unless acted upon by a resultant force . Velocity is a vector quantity, so an object's velocity changes if its speed and/ or direction changes 1 of 12 Newton's third law of motion When two objects interact, they exert equal and opposite forces on each other . The forces acting on the interacting objects are always of the same type 2 of 12 The four fundamental forces Gravitational Electromagnetic Strong nuclear Weak nuclear 3 of 12 Linear momentum equation p (momentum) = m (mass) * v (velocity) 4 of 12 Principle of conservation of momentum For a system of interacting objects, the total momentum in a specified direction remains constant, as long as no external forces act on the system 5 of 12 Example of zero momentum A gun recoils when a bullet is fired . The momentum of the gun and the momentum of the bullet have the same magnitude but act in oppsite directions . The total momentum of the cloesed system remains the same and is equal to zero 6 of 12 Perfectly elastic collision Momentum conserved Total energy conserved Total kinetic energy conserved 7 of 12 Inelastic collision Momentum conserved Total energy conserved Total kinetic energy not conserved 8 of 12 Newton's third law of motion The net force acting on an object is directly proportional to the rate of change of its momentum, and is in the same direction . F (force) = Δp (change in momentum) / Δt (time) 9 of 12 Force equation F = Δp / Δt . F = (mv - mu) / t . F = m ((v-u) / t) . F = ma 10 of 12 Why momentum is conserved in collisions According to Newton's third law of motion, each object experiences an equal but opposite force . The net force acting on the objects in this closed system is zero . According to Newton's second law of motion, Δp / Δt = 0 . The change in momentum of both objects must be zero . The total momentum of the objects does not change . Momentum is always conserved 11 of 12 Impulse of a force The product of force and the time for which this force acts on an object . Change in momentum . The area under a force-time graph 12 of 12

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