TAKS Review - Formulas

1. TAKS Review - Formulas Integrated Physics and Chemistry (4) Science Concepts. The student knows concepts of force and motion evident in everyday life. The student is expected to: (A) calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines;

2. Common measurements and symbols

3. Using the formula chart 1. Circle what you are asked to find 2. Underline given facts with numbers and units and write the symbol above it. 3. Identify the formula(s) you will use from the formula chart 4. Rearrange the formula for what you’re asked to find. 5. Put in numbers for symbols and solve. 6. Check that you answered the question asked.

4. Rearranging formulas When a formula is not solved for the variable you are trying to find, then you need to rearrange it until your variable is alone on one side of the equation.

5. d v t Rearranging formulas Example, the speed formula is: If you are given speed and time and want to find distance, what would the formula be?

6. d v t d t t x v x d v x t t Rearranging formulas Here, you divided d by t. To move t to the other side, do the opposite, multiply by it. t cancels on the right side And you are left with the formula for d.

7. Speed and Velocity How fast an object is traveling. Velocity has direction, speed does not.

8. Acceleration The change in velocity Can be: • speeding up • slowing down • or changing direction If an object is moving at a constant speed, acceleration = 0 Negative acceleration (deceleration) means the object is slowing down.

9. Work Using force to move an object a certain distance. If there is no movement, there is no work done. If distance = 0, work = 0 The displacement must be in the direction of the force. Does not depend on the time it takes to do the work

10. If Distance = 0, then Work = 0.

11. The man is carrying his groceries 2 meters to the counter. He is holding the groceries with a force of 10 N, what is the work done on the groceries? The force and the displacement are not in the same direction. Therefore, Distance = 0, Work = 0. If the man had been lifting the groceries up, then there would be work.

12. Power The rate at which work is done. More power means the same work can be done faster.

13. How could this person increase his power?

14. What is the power of this motor? Power = Work/time Time = 5 s We must find the work first! Work = Force x distance = 10 N x 2m = 20 J Power = Work/time = 20J/5s =4 Watts

15. Momentum The product of an object’s mass and velocity. Can be thought of as how difficult it is to stop a moving object. A stopped object has zero momentum.

16. Conservation of Momentum In collisions, total momentum does not change. The momentum of the objects (together) before the collision is the same as the momentum of the objects (together) after the collision.

17. Distance vs. Time graphs • In a distance vs. time graph, the slope of the line is the speed of the object. • If you have a horizontal line, the object is stopped.

18. No speed = stopped

19. Constant speed away from a point Constant speed toward a point

20. The line gets less steep – slowing down The line gets steeper – speeding up

21. Velocity vs. Time Graphs • In a velocity vs. time graph, the slope of the line is the acceleration of the object. • In this type of graph, a horizontal line means that the object is moving at a constant speed.

24. 1. 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

25. 2. 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

26. 3. How much work is performed when a 50 kg crate is pushed 15 m with a force of 20N? F 300 J G 750 J H 1,000 J J 15,000 J

27. 4. According to this graph, what was the bicycle’s acceleration between 6 and 10 seconds? A 0.0 m/s2 B 0.65 m/s2 C 1.6 m/s2 D 6.5 m/s2

28. 5. 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

29. 6. 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 489 W B 1815 W C 4796 W D 30,294 W

30. 7.

32. 9.The pictures show how an air bag functions in a collision. How much momentum in kg.m/s does the air bag absorb from the crash-test dummy if all of the crash-test dummy’s momentum is absorbed by the air bag? P = m x v = 100 kg x 6.3 m/s = 630 kg x m/s

33. Integrated Physics and Chemistry (4) Science Concepts.The student knows concepts of force and motion evident in everyday life. The student is expected to:(B) Investigate and describe [applications of] Newton’s laws such as in vehicle restraints, sports activities, geological processes, and satellite orbits.

34. Forces • Force can be defined as a push or a pull. • Forces can be balanced, which mean they are equal and opposite with no change in direction. If the forces on an object are balanced, it will either remain at rest or it will move at a constant speed in a straight line.

36. Unbalanced forces cause an object to accelerate (speed up, slow down or change direction) in the direction of the largest force.

37. Friction is a force that acts in the opposite direction to the motion of a moving object.

38. Newton’s Laws Newton’s First Law: An object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an unbalanced force. • The Law of Inertia.

40. Orbits and Inertia

41. Newton’s Second Law: • Force = mass x acceleration • For a constant force, if mass increases acceleration decreases • For a constant mass, if force increases, acceleration increases

42. The force on the ball and the force on the cannon are equal (See 3rd Law). F = ma The ball’s mass is lower, so its acceleration is higher. The cannon’s mass is greater, so its acceleration is lower.

43. Newton’s Third Law: For every action force, there is an equal and opposite reaction force.

44. 1. Which of these is the best description of the action- reaction force pair when the space shuttle lifts off from the launchpad? A The ground pushes the rocket up while exhaust gases push down on the ground.B Exhaust gases push down on air while the air pushes up on the rocket.C The rocket pushes exhaust gases down while the exhaust gases push the rocket up.D Gravity pulls the rocket exhaust down while friction pushes up against the atmosphere.

45. 2. After shooting a cannonball, a cannon recoils with a much lower velocity than the cannonball. This is primarily because, compared to the cannonball, the cannon has a — F much greater massG smaller amount of momentumH greater kinetic energyJ smaller force applied to it

46. 3. How many newtons of force does a 50.0 kg deer exert on the ground because of gravity? F = m x a 50 kg x 9.8m/s2 = 490 N

47. 4. Which factor would most likely cause a communications satellite orbiting Earth to return to Earth from its orbit? F An increase in the satellite’s forward momentumG An increase in solar energy striking the satelliteH A decrease in the satellite’s sizeJ A decrease in the satellite’s velocity

50. TAKS Review: Simple machines (D) investigate and demonstrate [mechanical advantage and] efficiency of various machines such as levers, motors, wheels and axles, pulleys, and ramps. (11th only)