2Gravity Many types of forces act on objects. Gravity is an attractive force between all objects that have mass.
3GravityThe ball does not travel in a straight line because of the unbalanced force of gravity acting on it.
4The Law of Universal Gravitation The Law of Universal Gravitation states that all objects with mass are attracted to each other.The magnitude of attraction depends on the mass of each object and the distance between them.
5The Law of Universal Gravitation The gravitational force becomes stronger as either or both objects increase in mass.The gravitational force becomes weaker as the distance between the objects increases.
7Weight and MassMass is the amount of matter in an object and does not change with location.Weight is the gravitational force on a object and changes with location.
8Weight and Mass Weight is a force and a vector. Weight changes with height above Earth.The gravitational pull of the earth has been mapped in this new geoid image from the GOCE satellite - with the yellows and red indicating a strong pull, while the blues show less gravity.2011
10FrictionFriction is a force that opposes the movement between two surfaces in contact.
11Friction A book pushed across a table slows down because of friction. Friction is an unbalanced force acting on the book to slow it down.MOTIONFRICTION
12Friction Without friction, you could not walk, drive, skate, etc. Sometimes we want to INCREASE it. (cleats, surfboard wax)
13Static FrictionStatic friction is the force between two surfaces in contact that keeps them from sliding when a force is applied.
14Static FrictionA force is applied to a heavy box, but the box doesn’t move.
15Static FrictionThe forces are balanced, the force pushing the box equals the force of static friction pushing in the opposite direction.
16Sliding FrictionWhen the force pushing on the box is larger than the maximum static friction force, the box begins to slide.The frictional force that acts on the sliding box is called sliding friction.
17Sliding FrictionThe book pushed across the table slows down because of sliding friction.Without sliding friction, the book would continue moving without a force being applied.
18Sliding FrictionUsually friction is present and an unbalancing force must be applied to keep an object moving.When friction is greatly reduced, objects move with nearly constant velocity without an applied force.
19Rolling & Fluid Friction Rolling Friction – when an object rolls over a surface.Fluid Friction – when an object moves through a gas OR a liquid (a fluid).
20Elastic ForcesAn elastic force occurs when a material is stretched or compressed.A diving board exerts an upward elastic force on the diver when it is bent downward.2 types: tension and compression.
21Tension ForcesA tension force is a pulling force exerted by an object when it is stretched, such as a rubber band.
22Compression ForcesA compression force is a pushing force exerted by a material when it is squeezed or compressed.The size of the compression force exerted by a material is equal to the size of the force that compresses the material.
23Normal ForcesA normal force is the force exerted by an object that is perpendicular to the surface of the object.
24Normal ForcesThe cup is exerting a downward force on the table, caused by gravity.The table is exerting an upward normal force on the cup, caused by compression.
252.2 Types of ForcesA(n) ____ force is the force exerted by an object that is perpendicular to the surface of the object.A compressionB elasticC normalD tension
26Which force causes a rolling ball to slow down? A sliding friction 2.2 Types of ForcesWhich force causes a rolling ball to slow down?A sliding frictionB static frictionC normal forceD gravity
27The gravitational force between two objects ____ as ____ increases. 2.2 Types of ForcesThe gravitational force between two objects ____ as ____ increases.A increases; distanceB decreases; massC increases; velocityD decreases; distance
28ABCDIf a student pushes a book across a table with a force of 10 N and the force of friction is 2 N, what is the net force on the book?A 0 NB 2 NC 8 ND 12 N
29What balanced forces are acting on a book sliding across a table? SCI 2.dABCDWhat balanced forces are acting on a book sliding across a table?A gravityB gravity and frictionC sliding friction, normal force, and gravityD gravity and normal force