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## TAKS Objective 5

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**TAKS Objective 5**The student will demonstrate an understanding of motion, forces, and energy.**Speed**• Speed is the rate of change in position • V = d t • V = velocity • d = distance • t = time**Set up the Speed Triangle**V = d t d v t**Sometimes the question will use the word VELOCITYinstead of**speed. v = d t A 1-kilogram ball travels 50 meters in 5 seconds. The velocity of the ball is —**d**v t Speed = 56 meters 96 sec Speed = 0.58 m/s Exit 2009**Velocity & Speed**• Velocity is the speed and direction of an object • The velocity of an object can change even if the speed remains constant**Acceleration**• Acceleration is the rate of change of velocity • Speeding up • Slowing down**Equation to find Acceleration**vf - vi a = -------- t vf = final velocity vi = initial (beginning velocity) a = acceleration t = time vf - vi vf - vi a t a**vf - vi**a = (30 m/s) – (20 m/s) 2 seconds a = (10 m/s) 2 s a = 5 m/s2 t a Grade 10 2009**What is a force?**• Forces are all around us • Pushing • Pulling • Squeezing**Momentum**• Momentum can be defined as "mass in motion.” • Momentum depends upon the variables mass and velocity • Momentum = mass x velocity • p = m x v • m = mass • v = velocity • p = momentum p v m**Momentum**• Describe the momentum of a 5-kg bowling ball moving westward at 2 m/s. • p = m x v • p = 5 kg x 2 m/s • p = 10 kg x m/ s p m v**p = mv**p = 2.0 kg x 15 m/s p = 30 kg • m/s p m v Grade 10 2009**p**m v p = m x v p = 0.2 kg x 12 m/s p = 2.4 kg • m/s Exit 2009**ENERGY**Energy is the amount of work a physical system is capable of performing. The Law of Conservation of Mass states: Energy can neither be created nor destroyed**A measure of the change a force produces.**The work done by a force acting on an object is equal to the force multiplied by the distance through which the force acts. Work W F d**Work is done…**…by a force when the object it acts on moves a distance NO work is done by pushing against a wall that will not move. Work IS done throwing a ball because the ball MOVES while being pushed during the throw. Work**The Joule**• joule (J) • The SI unit of energy • Amount of work done by a force of one Newton when it acts through a distance of one meter:**A person pushes a large box across a level floor by applying**a horizontal force of 200 N. If the person pushes the box a distance of 5 meters in 10 seconds, how much work does the person do on the box? Practice Problem #1 Work =force x distance W=F x d A 2000 joules B 1000 joules C 400 joules D 100 joules W W= (200N)(5m) = 1000 joules F d**The weight lifter used a force of 980 N to raise the**barbell over her head in 5.21 seconds. Approximately how much work did she do in raising the barbell? F 380 J G 982 J H 2,000 J J 10,000 J W=F x d W= 980N x 2.04m =1999.2J W F d (Practice problem from TEA released TAKS Test)**The RATE of Doing Work…**• Power is the amount of work done in a specified period of time • The more powerful something is, the faster it can do work Power W P t**A mechanic used a hydraulic lift to raise a**12,054 N car 1.89 m above the floor of a garage. It took 4.75 s to raise the car. What was the power output of the lift? A 489W B 1815W C 4796 D 30,294W P=W / t W = F x d W=12,054N x 1.89m = 22,782.06J P= 22,782.06J/4.75s=4,796.2W W P t (Practice problem from TEA released TAKS Test)**Day 2**Newton’s Three Laws, Simple Machines, & Waves**1st Law of Motion (Law of Inertia)**An object at rest will stay at rest, and an object in motion will stay in motion, unless acted upon by an unbalanced force.**1st Law**• Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.**What is one type of unbalanced force that acts on an object**in motion? Friction!**Friction**Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of friction.**Don’t let this be you. Wear seat belts.**Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving forward at 80 km/hour. Newton’s 1st Law and You**The force of an object is equal to the product of its mass**and acceleration, or F=m x a. 2nd Law**F = m x a**2nd Law**How much force is needed to accelerate a 1400 kilogram car 2**m/sec2? • F = m x a • F = 1400 kg x 2 m/sec2 • 2800 N F 2ndLaw m a**What acceleration will result when a 12 N net force is**applied to a 3 kg object? F = m x a a = F = 12 N = 4 m/sec2 m 3 kg F m a Check Your Understanding**2. A net force of 16 N causes a mass to accelerate at a rate**of 5 m/s2. Determine the mass. F = m x a m = F = 16 N = 3.2 kg a 5 m/s2 F m a Check Your Understanding**3. How much force is needed to accelerate a 66 kg skier 1**m/sec2? F = m x a F = 66 kg x 1 m/sec2 F m a Check Your Understanding**4. What is the force on a 1000 kg elevator that is falling**freely at 9.8 m/sec2? F = m x a F = 1000 kg x 9.8 m/sec2 F = 9800 N F F m m a Check Your Understanding**W = (3 kg•m/s2) x (8.0 m)**W = 24 Nm F = (6.0 kg) x (0.50 m/s2) F = 3 kg • m/s2**3rd Law**• For every action, there is an equal and opposite reaction.**3rd Law**When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.**The hot gases push down against the ground. As the gases**move downward, the rocket moves in the opposite direction, upward. 3rd Law**What is a Simple Machine?**• A simple machine has few or no moving parts. • Simple machines make work easier**Wheels and Axles**• The axle is a rod that goes through the wheel which allows the wheel to turn • Gears are a form of wheels and axles**Pulleys**• Pulley are wheels and axles with a groove around the outside • A pulley needs a rope, chain or belt around the groove to make it do work**Inclined Planes**• An inclined plane is a flat surface that is higher on one end • Inclined planes make the work of moving things easier**Wedges**• Two inclined planes joined back to back. • Wedges are used to split things.