EJC Physics H204 Forces 2023_1. Notes (FULL)

A screw is a long inclined plane wrapped around an axis. A force (that is lower in magnitude) is exerted over a long distance along the “ramp” – it takes less effort to rotate the screw but you will need to make many rotations to secure the screw which will then provide a large retention force. Content • Types of force • Centre of gravity • Turning effects of forces • Equilibrium of forces • Upthrust Learning Outcomes Candidates should be able to: (a) show recall and apply Hooke’s law (F = kx, where k is the force constant) to new situations or to solve related problems (b) describe the forces on mass, charge and current in gravitational, electric and magnetic fields as appropriate (c) show a qualitative understanding of normal contact forces, frictional forces and viscous forces including air resistance (No treatment of the coefficients of friction and viscosity is required) (d) show an understanding that the weight of a body may be taken as acting at a single point known as its centre of gravity (e) define and apply the moment of a force and the torque of a couple (f) show an understanding that a couple is a pair of forces which tends to produce rotation only (g) apply the principle of moments to new situations or to solve related problems (h) show an understanding that, when there is no resultant force and no resultant torque, a system is in equilibrium. (i) use a vector triangle to represent forces in equilibrium (j) derive, from definitions of pressure and density, the equation p = ρgh (k) solve problems using the equation p = ρgh (l) show an understanding of the origin of the force of upthrust acting on a body in a fluid (m) state that upthrust is equal in magnitude and opposite in direction to the weight of the fluid displaced by a submerged or floating object (n) calculate the upthrust in terms of the weight of the displaced fluid (o) recall and apply the principle that, for an object floating in equilibrium, the upthrust is equal in magnitude and opposite in direction to the weight of the object to new situations or to solve related problems

Physics tries to understand all the different types of forces in the Universes using the fewest number of basic laws. We currently categorise all forces in terms of 4 fundamental interactions. force effects range gravitational force acts on all masses infinite electromagnetic force acts on electric charges infinite strong nuclear force acts on protons and neutrons holds them together in an atomic nucleus 1510− m weak nuclear force acts on elementary particles results in radioactive decay 1710− m Force is a vector quantity. It has both magnitude and direction. In recognition of Isaac Newton’s work on classical mechanics, specifically Newton’s 2 nd Law of motion (see topic on Dynamics), the SI unit of force is the newton (N). 1 N is the magnitude of a force that acts on a mass of 1 kg resulting in an acceleration of 1 m s-2 in