TAKS Objective 5

1. TAKS Objective 5 Motion , Forces and Energy

2. 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!

3. Griddable Answers 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.

4. Definition of a Force • A Force is a push or a pull

5. Balanced Force • A force that produces no change in an object’s motion because it is balanced by an equal, opposite force. Unbalanced Forces cause changes in motion

6. 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

7. 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

8. 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.

9. 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 = WoutX 100% Win

10. 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

11. 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

12. 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:

13. 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

14. 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!

15. 4B • investigate and describe applications of Newton's laws such as in vehicle restraints, sports activities, geological processes, and satellite orbits

16. Friction Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat.

17. 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

18. 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

19. 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

20. 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

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

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

23. 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

25. 4D • investigate and demonstrate mechanical advantage and efficiency of various machines such as levers, motors, wheels and axles, pulleys, and ramps

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

27. 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!

28. 6 Types of simple machines • Inclined planes • Screws • Pulleys • Wheel and axle • Levers • Wedge

29. 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

30. 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

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

32. 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

33. Waves - 2 Types

34. 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

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

36. 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

37. 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

42. 6A • describe the law of conservation of energy

43. 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.

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

45. 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!!

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

49. 6B • investigate and demonstrate the movement of heat through solids, liquids, and gases by convection, conduction, and radiation

50. 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. . .