3 Newton’s First Law of Motion 1st Law of Motion(Law of Inertia)Objects in motion will stay in motion in a straight lineand objects at rest will stay at rest, unless acted on byan outside forceEx. Stack of books on a car seat. What happenswhen you suddenly stop?
4 Inertia - objects resistance to a change in motion Mass affects an objects inertiaIncrease mass =Increase inertiaLower mass =Lower inertia
5 Seat belts and inertiaSeat belts work because they keep your body from flying forward.If you get hit from behind will seatbelts or air bags help?No, you will fly back into theseat.
6 Newton’s Second Law of Motion Force is equal to the mass of an object and its acceleration.Force = Mass x AccelerationF = m x aForce is measured in Newtons1 N = 1 kg x 1 m/s2 or 1kgm/s2( 1 lb is = to 4.45 N or 1 N is = to .225 lb)
7 Newton’s Second Law of Motion Newton’s second law explains how acceleration is dependant on force and mass.
9 Newton’s Second Law of Motion Newton’s second law could also be written as: - When a force is applied to an object, the object accelerates in the direction of the greater force.ORThe acceleration of an object is directly proportional to the net force on the object and inversely proportional to the object’s mass.
10 Newton’s Second Law of Motion Acceleration = net force/massor a = F/m
12 Gravity Gravity - Force of attraction between two objects. - force of gravity depends on two variables:a. depends on masslarger = more gravity (attraction)smaller = less gravity (attraction)
13 Gravity - force of gravity depends on two variables:(continued) b. depends on distancecloser = more gravity (attraction)- further = less gravity (attraction)
14 Weight A measurement that can be taken because of gravity is weight. Weight – force of gravity pulling on the mass of an object.- weight is a force that can change. Mass never changes!
15 Free Fall when only gravity is acting on a falling object. constant rate of acceleration. This is called gravitational acceleration (g)* g = 9.8 m/s²- which means everything accelerates as it falls at the rate of 9.8 m/s² each second!
16 Free Fall and WeightWe can use this knowledge to mathematically find weight!Equation to find weight is same as force!Force (weight) = m aorweight = m X g (acceleration of gravity)
18 Weight Ex. Find the weight of a 58 kg man on Earth. Weight = 58kg x Weight = mgWeight = 58kg x10 m/s2= 580 kg m/s2 or 580 NNow find his weight on:Venus g=8.8 m/s2Mars g= 3.7 m/s2Neptune g=11.8 m/s258kg x 8.8 m/s2 = 510N58kg x 3.7 m/s2 = 220N58kgx11.8 m/s2 = 680N
19 Newton’s 2nd LawNewton’s 2nd law explains why heavy objects and light objects fall at the same rate.-because if the mass is large, it is harder to accelerate (has more inertia).So it takes more time to fall!
20 Terminal Velocity On Earth we have air resistance - causes friction, causing the falling objects to slow downTerminal Velocity- maximum velocity reached by a falling object (320 km/h or 120 mph)- occurs when air resistance is equal to the gravitational acceleration.
22 Projectile Motioncurved path an object follows when projected near the Earth’s surface.
23 Projectile Motion- 2 components make up the path of projectile motion.Both are independent of each other.a. horizontal motion-force stays constantvertical motion-pulling it down at a rate of 9.8 m/s2
24 Projectile MotionWhat if your object you are shooting at is falling too.Where should you aim?
25 Projectile Motion -Orbiting objects are in projectile motion. - so they are NOT weightless or floating, they are just constantly falling!
26 Newton’s 3rd Law of Motion For every action there is an equal and opposite reaction.Forces act in pairs- don’t necessarily act on the same objects.Ex. Escaped balloonAction – air escaping from opening in balloonReaction - balloon flies forward.
27 Momentum The product of the mass and velocity of a moving object. Momentum(p) = mass (kg) x velocity (m/s)p = kgm/sEx. Calculate the momentum of a 6.00kg bowling ballMoving at 10.0 m/s down the lane.6.00kg x 10 m/s = 60.0 kgm/s down the lane
28 The Law of Conservation of Momentum Total amount of momentum in a system is conserved.Ex.