Published on March 8, 2014
NEWTON’S LAWS AND APPLICATION OF NEWTON’S LAWS Grade 11
MECHANICS GRADE 11 CONTENT 1.Newton’s laws of motion 2.Applications of Newton’s Laws 3.Newton’s law of Universal Gravitation 4.The kinds of Forces
RECAPPING ON WHAT WE KNOW PREVIOUSLY…. Speed & Velocity • Speed - the rate of change in position over time (distance/time) • Instantaneous speed-(physics) a scalar measure of the rate of movement of a body expressed as the rate of change of position with respect to time at a particular point • Average speed- The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval • How is velocity different from speed?
Change in Velocity • What makes an object change velocity? Acceleration • Acceleration is how quickly velocity changes over a certain time.
First Law: An object at rest will stay at rest unless acted on by an unbalanced force. An object in motion will continue to move in the same direction with the same speed unless an external force causes a change in the objects speed.
INERTIA • tendency of an object to resist any change in its motion • increases as mass increases
• Second Law: Force causes an object to accelerate while the object’s mass resists acceleration. BUT
For every action, there is an equal and opposite reaction. • Forces occur only in pairs • • Act on different objects Equal and opposite
Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.
FORCES: DEFINITION, CATEGORIES, A ND TYPES.
DEFINITION OF A FORCE A force is a push or pull upon an object that occurs because when that object interacts with another object Forces ONLY exist when there is interaction. Keep in mind that objects includes anything and everything, including the Earth
Measured in Newton One Newton is the amount of force required to give an object of 1Kg an acceleration of 1 m/s². A force is a vector quantity (has to have a direction)
CATEGORIES OF FORCE 1. Contact Force: The types of forces that occur when two objects are said to be in physical contact with each other. 2. Action-at-a-Distance Force/Non-Contact Forces: Forces that result even when two interacting objects are not in physical contact with each other.
CONTACT FORCES 1.Frictional Force 2.Tension Force 3.Normal Force 4.Air Resistance Force 5.Applied Force 6.Spring Force
NON-CONTACT FORCES 1. Gravitational Force 2.Electrical Force 3. Magnetic Force
CONTACT FORCES 1.FRICTIONAL FORCE; Friction is a force that opposes relative motion between two surfaces in contact.Friction is caused by the interlocking of the surfaces and attractive force between the surface molecules. Friction is represented by the following equation; Ffrict = µ • Fnorm Where µ is the co-effient of friction and can either be static or kinetic
CONTACT FORCES CONT.… 2. Tension Force; Ftens The tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends. The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.
CONTACT FORCES CONT.… 3.Normal Force: The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. On occasions, a normal force is exerted horizontally between two objects that are in contact with each other. For instance, if a person leans against a wall, the wall pushes horizontally on the person. 4.Air Resistance Force The air resistance is a special type of frictional force that acts upon objects as they travel through the air. The force of air resistance is often observed to oppose the motion of an object. This force will frequently be neglected due to its negligible magnitude (and due to the fact that it is mathematically difficult to predict its value). It is most noticeable for objects that travel at high speeds (e.g., a skydiver or a downhill skier) or for objects with large surface areas
CONTACT FORCES CONT… 5.Applied Force: An applied force is a force that is applied to an object by a person or another object. If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person 6.Spring Force: The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position. For most springs (specifically, for those that are said to obey "Hooke's Law"), the magnitude of the force is directly proportional to the amount of stretch or compression of the spring.
FREE BODY DIAGRAM It is the diagram used to describe the forces acting on an object and in which direction they are acting on it. It shows the relation between the magnitude and the direction of the forces. ●Normal Force ●Gravitational Force ●Applied Force ●Frictional Force ●
REFERENCES Force by Lightkcse on Jul 23, 2013 available on : http://www.slideshare.net/Lightkcse/force-24549200?qid=aa7ebcb9-4408-4b869034-1f14d36f008b&v=default&b=&from_search=5 accessed:08/03/14 12:30pm Newton's law of gravitation by itutor on May 27, 2011available on : http://www.slideshare.net/itutor/newtons-law-of-gravitation21980823?qid=b482e799-3095-49ab-9fdd3e6c7b58ee06&v=qf1&b=&from_search=3 accessed:08/03/14 1:08pm Physics by Sahil Patel on Nov 16, 2013 available on : http://www.slideshare.net/morrispatel/physics-28323398?qid=ad9be860-3cf2-40ddab63-307f5c0fbd53&v=qf1&b=&from_search=2 accessed:08/03/14 11:00am MOTION (force & motion) (Teach) by Moira Whitehouse, Teacher retired at home on Oct 05, 2011available on : http://www.slideshare.net/MMoiraWhitehouse/motionforce-motion?qid=7f2e2ed5-6365-4006-a1cb4ba6567a3e95&v=qf1&b=&from_search=11 ccessed:08/03/14 10:40am Force and motion by Nimra Waheed, Working at Studying on Jan 04, 2014 available on : http://www.slideshare.net/nimrawaheed50/force-and-motion29685022?qid=5b1c9635-4b5f-489b-a35f-7611e82cc0a3&v=qf1&b=&from_search=1 ccessed:08/03/14 2:30pm
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