Why things move - Introduction to Physics - Lecture Slides | PHYS 1030, Study notes of Physics

Download Why things move - Introduction to Physics - Lecture Slides | PHYS 1030 and more Study notes Physics in PDF only on Docsity! Ch 4 Why things move • Force – external influence that causes a body to accelerate A force is an action that one object does to another. examples: – Pulling on a rope produces a tension force. – The mass of the earth pulls down on you, producing your weight. net force The net force is the sum of all the forces acting on an object. (Need to consider direction.) F1F2 Fnet F1 FnetF2 Only the component of force that is parallel to the motion accelerates the object. The component of gravity that is along an incline accelerates the object that goes down the incline. The steeper the incline, the larger the acceleration. weight component of weight parallel to incline weight – net gravitational force acting on an object by all other objects normal force – a force that is exerted on one object by another by physical contact. Normal means perpendicular. Normal forces are perpendicular to the surface of contact. Force pairs • Forces always act in pairs. • examples are: – swimming – jet airplane – plane and boat propellers – Rockets Rocket motion Rocket motion involves the law of force pairs. When a rocket forces gas out of its engine it exerts a force on the gas. The gas exerts an equal and opposite force on the rocket. Example of being stranded on a frozen pond. You can get off the ice if you behave ‘like a rocket’. Gravitation • Force of gravity between any two objects See graph on page 96 2 21 separation massmass F 2 2111107.6 d mm xF