Physics Chapter 2 Motion PDF

Because learning changes everything. ® Chapter 2 Motion © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of...

Because learning changes everything. ® Chapter 2 Motion © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Overview Description: Explanation: Position. Forces. Velocity. Newton’s laws. Acceleration. Applications: Horizontal motion on land. Falling objects. Compound (2-D) motion. Momentum. Circular motion. Newton’s law of gravitation. © McGraw Hill 2  Measuring motion Two fundamental Three important combinations components: of length and time: Change in position. Speed. Change in time. Velocity. Acceleration. © McGraw Hill 3  Speed Change in position with respect to time. distance speed  Average speed - most time common measurement. distance The bar means "average" Instantaneous speed - time interval d v= t approaches zero. Average speed time © McGraw Hill 4  Example: average speed Calculate average speed between trip times of 1 hour and 3 hour d ? v  t ? 150 kilometers  50 kilometers 50 kilometers v  2 hours hour © McGraw Hill 5  Velocity Describes speed (How fast is it going?) and direction (Where is it going?) Graphical representation of vectors: length = magnitude; arrowheads = direction. © McGraw Hill 6  Acceleration Rate at which motion changes over time. Speed can change. Direction can change. Both speed and direction can change. change in velocity v acceleration   time elaosed t V fi  V a t © McGraw Hill 7  Forces - historical background Aristotle Galileo and Newton Heavier objects fall faster. All objects fall at the same rate. Objects moving horizontally No force required for require continuously uniform horizontal motion. applied force. Reasoning based upon Relied on thinking alone. measurements. © McGraw Hill 8  Force A push or pull capable of changing an object’s state of motion. Overall effect determined by the (vector) sum of all forces - the “net force” on the object. Access the text alternative for slide images. © McGraw Hill 9  Four Fundamental Forces Gravitational Act between all objects. Electromagnetic Act between electrically charged parts of atom. Weak Nuclear Force Involved in certain nuclear reactions. Strong Nuclear Force Involved in hold nucleus together. Stronger than electromagnetic and gravitational force. © McGraw Hill 10  Horizontal motion on land “Natural motion” question: Is a continuous force needed to keep an object moving? No, in the absence of unbalanced retarding forces. Inertia - measure of an object’s tendency to resist changes in its motion (including rest). © McGraw Hill 11  Balanced and unbalanced forces Motion continues unchanged without unbalanced forces. Retarding force decreases speed. Boost increases speed. Sideways force changes direction. © McGraw Hill 12  Falling objects Free fall - falling under influence of gravity without air resistance Distance proportional to time squared Velocity increases at constant rate Acceleration due to gravity (g) same for all objects 2 98 meters second 32 feets second 2  © McGraw Hill 13  Compound motion Three types of motion: Projectile motion: Vertical motion. An object thrown into Horizontal motion. the air. Combination of 1 and 2. Basic observations: Gravity acts at all times. Acceleration (g) is independent of the object’s motion. © McGraw Hill 14  Projectile motion Vertical projectile Slows going up. Stops at top. Accelerates downward. Force of gravity acts downward throughout. Horizontal projectile Horizontal velocity remains the same (neglecting air resistance). Taken with vertical motion = curved path. © McGraw Hill 15  Fired horizontally versus dropped Vertical motions occur in parallel. Arrow has an additional horizontal motion component. They strike the ground at the same time! Access the text alternative for slide images. © McGraw Hill 16  Example: passing a football Only force = gravity (down) Vertical velocity decreases, stops and then increases Horizontal motion is uniform Combination of two motions = parabola Access the text alternative for slide images. © McGraw Hill 17  Three laws of motion First detailed by Newton (1564 to 1642 AD). Concurrently developed calculus and a law of gravitation. Published Principia. Essential idea – forces. © McGraw Hill 18  Newton’s 1st law of motion “The law of inertia.” Every object retains its state of rest or its state of uniform straight-line motion unless acted upon by an unbalanced force. Inertia resists any changes in motion. © McGraw Hill 19  Newton’s 2nd law of motion Forces cause accelerations. Units = Newtons (N). Fnet ma Proportionality constant = mass. Fnet More force, more acceleration. a m More mass, less acceleration. © McGraw Hill 20  Examples - Newton’s 2nd © McGraw Hill 21  Weight and mass Mass = quantitative measure of inertia; the amount of matter. Weight = force of gravity acting on the mass. Pounds and newtons measure of force. Kilogram = measure of mass. © McGraw Hill 22  Newton’s 3rd law of motion Source of force - other objects FA due to B FB due to A 3rd law - relates forces between objects “Whenever two objects interact, the force exerted on one object is equal in size and opposite in direction to the force exerted on the other object.” © McGraw Hill 23  Momentum Important property closely related to p mv Newton’s 2nd law Includes effects of both motion (velocity) and inertia (mass) © McGraw Hill 24  Conservation of momentum According to the law of conservation of momentum, the momentum of the expelled gases in one direction equals the momentum of the rocket in the other direction in the absence of external forces. Access the text alternative for slide images. © McGraw Hill 25  Impulse A force acting on an object for some time t An impulse produces a change in momentum Applications: airbags, padding for elbows and knees, protective plastic barrels on highways impulse = Ft p  Ft Access the text alternative for slide images. © McGraw Hill 26  Forces and circular motion Circular motion = accelerated motion (direction v2 changing). ac  r Centripetal acceleration present. v2 Centripetal force must be Fc mac m r acting. Centrifugal force - apparent outward tug as direction changes. Centripetal force ends: motion = straight line. Access the text alternative for slide images. © McGraw Hill 27  Newton’s law of gravitation 1 Attractive force between all masses Proportional to product of the masses Inversely proportional to separation  11 2 G 6.67 10 N m kg distance squared  Gm m Explains why F  12 2 d g  meters second 2 mass cancels   Provides centripetal force GmM for orbital motion. F  2 Earth mg r Earth GM Earth m g 9.8 r 2 Earth s2 Access the text alternative for slide images. © McGraw Hill 28  Newton’s law of gravitation 2 Earth Satellites: A cannonball shot with sufficient speed from a mountaintop will orbit Earth. With the correct tangential speed, and above the atmosphere and air friction, satellites follow a circular orbit for long periods of time. Geosynchronous satellites orbit the earth at an altitude of 36,000 kilometers and have a period of 1 day, so they appear not to move. © McGraw Hill 29  Newton’s law of gravitation 3 Weightlessness Skydivers and astronauts experience apparent weightlessness because all objects in freefall accelerate with a force of g. To experience true weightlessness, one would have to travel far from Earth and its gravitational field, and far from the gravitational fields of other planets. © McGraw Hill 30  End of Main Content Because learning changes everything. ® www.mheducation.com © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.