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Forces Chapter 10 Mrs. Yakulis 8th Grade Name__________________ Section 1 Nature of Forces Force is a _____________ Has _______________ (size) Measured in ________________ (after Isaac Newton) Does not have to result in motion if __________________ Magnetism, electricity and gravity all exert forces that we cannot see Combination of forces is called ______________ Forces in the same direction _________________ Forces in different directions _________________________ The _______________ always acts in the direction of the ______________ If net force is not zero, force is __________________________ If net force is zero, force is balanced____________________________ Unbalanced forces are needed to change _________________ (direction and speed of an object) Balanced forces do not __________________________________ Section 2 Friction, Gravity and Elastic Force Friction: Force that _________________________ that are touching Amount of friction is determined by _________________ (rougher, more friction) and ___________________ (greater force, more friction) Types of friction ______________ _________________ (wheels, ball bearings) _____________________ (gases and liquids) ______________________ (balanced forces, no movement until force applied) Reduce: make surface smoother, use lubricants, ______________________ Increase: make surfaces rougher, _______________________________ Gravity Force of attraction of objects (pull) due to ________________________________ Matter has mass: Amount of _____________________ SI unit is _____________________ Is also a measure ______________________: Tendency of an object to _______________ in motion Large mass, more inertia (_______________________) Weight: ____________________ from mass Measure of _______________________ Force of attraction due to mass (pull) SI unit for force is ___________________ 1N= ________________________ Measured with a ______________________________ Weight = mass x _________________________ 1Newton= kg x m/s2 Weight will vary at other places in ________________________ Isaac Newton noticed the same force for a falling apple as _________________________________________________________ Law of Universal Gravitation • Formula: • G is a constant, m1 is mass of first object, m2 is mass of second object and r is distance between them •All objects fall at the same ______________________• ___________________ leaning tower of Pisa • Dropped cannonballs of ________________ • Land at ___________________________ • • • A___________________________________ TO PRODUCE THE SAME ACCELERATION F=_______________ A=F/M • All objects accelerate towards Earth at a rate __________________ •Air resistance slows down ____________________ • ___________________also known as air resistance • Depends on _____________________ of object •Acceleration stops at ______________________________ • As objects fall, air resistance increases until ________________________________ • Object continues to fall, but at a constant ________________________________ • ___________________ (acceleration due to gravity) means that object is falling with ____________________ (such as air resistance) acting on it except ______________ • • • • Astronauts appear to be __________________ due to “freefall” in orbiting spacecraft ________________________ = traveling in circular path _______________________________ combine to form an orbit This is an _________________ force because it changes the __________of an object Centripetal Force •_____________ = unbalanced force which causes __________ motion (__________ provides this force) •Centripetal means ______________________•____________ is an example of __________________ • Curved path when horizontal velocity combines with vertical acceleration • Examples: (gravity) • • • ___________Hopping ___________________ Water sprayed _____________________ Momentum • A property that depends on _____________________ • More momentum, harder to ________________________ • Mass * velocity • ____________________ •Law of _________________ of momentum • Momentum is ______________________ • __________________ forces are equal and opposite • Billard balls • Bowling •Compression force- elastic ____________________ matter together • _________________- elastic force that stretches or pulls matter