Motion , Forces and Energy TAKS Objective 5 Motion , Forces and Energy

4A calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines Use the formula chart to help determine these answers!

Griddable Answers . 1 2 3 4 5 6 7 8 9 Some of the problems require you to grid in an answer. Make sure you pay attention to the decimal point in the square in the middle.

Definition of a Force A Force is a push or a pull

Balanced Force A force that produces no change in an object’s motion because it is balanced by an equal, opposite force. If you were to add these forces they would = 0 Unbalanced Forces cause changes in motion

Work Work: using a force for a distance W = F x d The work done by forces on an object = changes in energy for that object. Work and Energy are measured in Joules

How much work is performed when a 50 kg crate is pushed 15 m with a force of 20 N? F 300 J G 750 J H 1,000 J J 15,000 J Use the formula Work = Force x distance Force of 20 N x 15 meters = 300 Joules

The diagram represents the total travel of a teacher on a Saturday The diagram represents the total travel of a teacher on a Saturday. Which part of the trip is made at the greatest average speed? F Q G R H S J T How do we work this one? Calculate v = d/t for each segment.

Real Machines use Energy No real machine is 100 % efficient. i.e. none put out more work than is put in Efficiency of a machine is work output/work input X 100 % Eff = Wout X 100% Win

The diagram shows an electric motor lifting a 6 N block a distance of 3 m. The total amount of electrical energy used by the motor is 30 J. How much energy does the motor convert to heat? F 9 J G 12 J H 18 J J 21 J See Next Slide for Answer

Work Input = 30J done by the motor Work Output = Resistance Force x Resistance Distance Workout = 18J = 6N x 3m The difference is lost as heat due to friction, which is 30J – 18J = 12J Answer G

A ball moving at 30 m/s has a momentum of 15 kg·m/s A ball moving at 30 m/s has a momentum of 15 kg·m/s. The mass of the ball is — A 45 kg B 15 kg C 2.0 kg D 0.5 kg Formula Page says that Momentum = Mass x Velocity So 15 kg.m/s = M x 30 m/s solving for M it is:

An advertisement claims that a certain truck has the most powerful engine in its class. If the engine has more power, which of the following can the truck’s engine do, compared to every other engine in its class? F Produce fewer emissions G Operate more efficiently H Perform work faster J Accelerate longer HINT: Look at the formula for Power

HINT: An object in motion can have a constant velocity, constant momentum, and constant acceleration BUT it cannot travel any distance other than ZERO & still be at rest!

4B investigate and describe applications of Newton's laws such as in vehicle restraints, sports activities, geological processes, and satellite orbits

Friction Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat. Air resistance is an another example of friction. Lubricants or grease reduce friction.

Newton’s 1st Law of Motion Object in motion stays in motion And Objects at rest stay at rest Unless acted upon by an unbalanced force

Inertia or Newtons 1st Law Tendency for an object to stay at rest or keep moving in a straight line at a constant speed. The mass (m measured in kg) of an object determines its inertia More mass = more inertia Inertia comes from the Latin word meaning lazy.

Newton’s 2nd Law of Motion The greater the mass of an object, the greater the force required to change its motion. F = m X a

Formula chart says F=ma, m is mass in kg, a is acceleration in m/s2. The frog leaps from its resting position at the lake’s bank onto a lily pad. If the frog has a mass of 0.5 kg and the acceleration of the leap is 3 m/s2, what is the force the frog exerts on the lake’s bank when leaping? A 0.2 N B 0.8 N C 1.5 N D 6.0 N Formula chart says F=ma, m is mass in kg, a is acceleration in m/s2. So, .5 kg x 3 m/s2= 1.5 N

Newton’s 3rd Law of Motion For every action force there is an equal and opposite reaction force.

Newton’s 3rd Law of Motion All forces come in action-reaction pairs Ex: feet push backward on floor, the floor pushes forward on feet

Starting from rest at the center of a skating rink, two skaters push off from each other over a time period of 1.2 s. What is the force of the push by the smaller skater? F 16 N G 32 N H 88 N J 100 N Newton’s 3rd law states that forces are equal & opposite in direction

4D investigate and demonstrate mechanical advantage and efficiency of various machines such as levers, motors, wheels and axles, pulleys, and ramps

Machines use power Power: the rate at which energy is used (work is done) P=Work/time Power is measured in watts

If a force of 100 newtons was exerted on an object and no work was done, the object must have — A accelerated rapidly B remained motionless C decreased its velocity D gained momentum Work = Force x Distance Work = 0 Force = 100 N so 0 J = 100 N x d distance must be 0 It did not move!

6 Types of simple machines Inclined planes Screws Pulleys Wheel and axle Levers Wedge

The diagram shows an electric motor lifting a 6 N block a distance of 3 m. The total amount of electrical energy used by the motor is 30 J. How much energy does the motor convert to heat? F 9 J G 12 J H 18 J J 21 J

Which configuration of pulleys and belts shown below will result in the fastest rotation of Spindle 2? HINT: Both spindles have to travel the same distance over the same time (speed = d/t) SO Larger spindle #1 will cause a smaller spindle #2 to travel faster

HINT: Work = Force x Distance Which diagram has equal amounts of work done on each side of the lever?

5A & 5B demonstrate wave types and their characteristics through a variety of activities such as modeling with ropes and coils, activating tuning forks and interpreting data on seismic waves; demonstrate wave interactions including interference, polarization, reflection, refraction, and resonance within various materials

Waves - 2 Types

Transverse Waves Particles vibrate at right angles to the direction the wave travels. (up & down motion) Ex. E. M. Waves, waves on a slinky or rope coil, ocean waves

Longitudinal or Compression Waves Vibrating particles move back and forth along the direction of the wave velocity Parts consist of compressions and rarefactions

All waves have similar properties Frequency- the number of vibrations per second or the speed of the movement of the vibrating particles Frequency = pitch of sound = color of light Amplitude – the size of the movement of the vibrating particles Amount of energy Ex: increased amplitude = louder sound = brighter light Resonance – vibration in one object causes a vibration in another nearby object

Velocity: v=f λ f-frequency and λ is wavelength (distance between identical points on two consecutive waves) Reflection- bounce off barriers in regular ways Refraction- waves can change direction when speed changes = bending of wave

6A describe the law of conservation of energy

Law of Conservation of Energy Energy can change forms, but is never created nor destroyed Loss in one form = gain in an another form A falling object speeds up as it falls to the ground; PE decreases as KE increases. The KE it has at impact = the PE it had before it fell.

Energy can be conserved all forms The chemical energy in a battery transforms into electrical energy

Energy Kinetic (Energy of Motion) and Potential (Stored Energy) Is defined as the Ability to do Work Energy has Two Types: Kinetic (Energy of Motion) and Potential (Stored Energy) Use the formula chart!!

Use the formula page! PE = mgh g=gravity = 9.8 m/s2

6B investigate and demonstrate the movement of heat through solids, liquids, and gases by convection, conduction, and radiation

Heat- Transfer of Thermal Energy Three forms of heating: 1. Conduction- direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And. . .

3. Radiation – Transfer of Electromagnetic (E.M.) Energy Objects are heated when exposed to infrared radiation The sun’s heats the earth by sending infrared radiation along with other forms of E.M. energy

6D investigate and compare economic and environmental impacts of using various energy sources such as rechargeable or disposable batteries and solar cells

Nuclear Reactions Fusion occurs when two atoms combine to form a new element. The sun produces all of its energy through fusion. Fission is the splitting of nucleii of large atoms such as Uranium and Plutonium

Which of these produces most of the compounds responsible for causing acid rain? A Nuclear fission B Fossil fuels C Solar cells D Windmills

6E investigate and compare series and parallel circuits

Series Circuits Series circuits are the most simple. One (1) path for the current to travel. Contains an energy source, a path, and a load (something for it to do, like a lamp)

Parallel Circuits Parallel circuits provide more than one path for the current to travel. Most circuits are parallel, since if one lamp goes out, the others can stay lit.

For Voltage Mathematics - USE THE FORMULA SHEET!! What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9 volt electrical source? A. 0.22 amp B. 4.5 amps C. 11.0 amps D. 18.0 amps V = I R V = voltage = volts I = current = amps R = resistance = ohms 9V = I x 2 ohms or 4.5 amps

Which circuit is built so that if one light bulb goes out, the other three light bulbs will continue to glow? HINT: Check to see which ones have complete pathways for each bulb!

Now You Try It!

Remember: must have complete pathways

When a DVD is read, laser light touches the DVD surface and is then measured at location A. What allows light to return to location A after striking the DVD surface? F Conduction G Refraction H Magnification J Reflection

An empty cup was tightly covered with plastic wrap, and a few grains of salt were sprinkled on top of the plastic. When a tuning fork was struck and placed slightly above the plastic wrap, the salt began to move. Which characteristic of waves does the movement of the salt best demonstrate? A Echo formation B Diffraction C Resonance D Specular reflection

HINT: All the types of radiation MUST equal the radiation coming in Assuming the chart contains all energy transformations in the Earth system, how much solar radiation goes toward evaporating water? F 40,000 terajoules G 92,410 terajoules H 121,410 terajoules J 133,410 terajoules

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

What is the net force exerted on a 90.0 kg race-car driver while the race car is accelerating from 0 to 44.7 m/s in 4.50 s? F 9.8 N G 20 N H 201 N J 894 N

When the air is released from a balloon, the air moves in one direction, and the balloon moves in another direction. Which statement does this situation best illustrate? F What goes up must come down. G For every action there is an equal and opposite reaction. H The shape and size of an object affect air resistance. J The acceleration due to Earth’s gravity is 9.8 m/s 2.