Physics: Representing Forces - Newton's Laws and Types | PDF

PHYSICS Exploration 1– Representing Forces  What is a force? A force is a “push” or a “pull”. Some common examples: WEIGHT – pulls things downwards  What is a force? A force is a “push” or a “pull”. Some common examples: An equal and opposite fo...

PHYSICS Exploration 1– Representing Forces  What is a force? A force is a “push” or a “pull”. Some common examples: WEIGHT – pulls things downwards  What is a force? A force is a “push” or a “pull”. Some common examples: An equal and opposite force, perpendicular to the surface (at right angles to) prevents the man from penetrating the surface  What is a force? A force is a “push” or a “pull”. Some common examples: AIR RESISTANCE (drag) – acts against WEIGHT – pulls anything moving through air things downwards FRICTION – acts against anything moving UPTHRUST – keeps things afloat Forces are vector quantities because they have both size and direction. Forces are vector quantities because they have both size and direction. SI units Forces are measured in newtons (N) Forces are vector quantities because they have both size and direction. SI units Forces are measured in newtons (N) Small forces can be measured using a spring balance (or newton meter) Newton’s first law of motion If no external force is acting on it, and object will: - If stationary, remain stationary - If moving, keep moving at a steady speed in a straight line.  Newton’s first law of motion If no external force is acting on it, and object will: - If stationary, remain stationary - If moving, keep moving at a steady speed in a straight line. In space, where there are no external forces, a satellite will continue to move at a steady speed in a straight line …. for ever! Balanced forces If forces are in balance, then they cancel each other out, and the object behaves as if there is no force on it at all  Balanced forces If forces are in balance, then they cancel each other out, and the object behaves as if there is no force on it at all When terminal velocity is reached, the skydiver is falling at a steady speed. The force of air resistance is exactly balanced by the air resistance pushing upwards.  Balanced or unbalanced forces? What will A happen in each case? B C D Balanced and Unbalanced Forces Balanced forces: If the forces acting on an object are balanced then the object will either remain stationary or continue to move with a constant speed. Balanced and Unbalanced Forces Balanced forces: If the forces acting on an object are balanced then the object will either remain stationary or continue to move with a constant speed. Unbalanced forces: If the forces acting on an object are unbalanced then the object will change its speed. It will begin to move, speed up, slow down or stop. Contact and Non Contact Forces Example Friction and Stopping Forces  Friction and Stopping Forces Although it is sometimes unwanted, friction can really help us – for example in car braking systems, and giving shoes grip on the ground.  Friction and Stopping Forces Although it is sometimes unwanted, friction can really help us – for example in car braking systems, and giving shoes grip on the ground. As the block is gently pulled, friction stops it moving – increase the force and the block will start to slip = starting or static friction.  Friction and Stopping Forces Although it is sometimes unwanted, friction can really help us – for example in car braking systems, and giving shoes grip on the ground. When the block starts to move, the friction drops. Moving or dynamic friction is less than static friction. This friction HEATS materials up.