STAAR Reporting Category 2 Force, Motion, & Energy

1. STAAR Reporting Category 2Force, Motion, & Energy Middle School Science Science STAAR Need to Know Science STAAR Need to Know

2. Journal Entry

4. Problem: In which position does the ball have the greatest kinetic energy and least potential energy?

5. Claim:

6. Scientific Explanation: Position 2 The closer the ball is to the ground, the greater is its kinetic energy and the least is its potential energy. The further away the ball is from the ground, the greater is its potential energy and the less is its kinetic energy.

7. Force is a push or pull.

8. PCES A teenager pulls a rope to the left with a force of 12 N. A child pulls on the other end of the rope with a force of 7 N. The child’s friend adds a force of 8 N, also pulling to the right. What will happen? A.The net force will be 3 N to the right. B.The net force will be 15 N to the left. C.The net force will be 12 N to the right. D.The net force will be 27 N to the left.

9. 12N 7N 8N What is the magnitude of the force, and in which direction will it move? Problem:

10. Claim:

11. 12N 15N Answer is 3N Scientific Explanation: A

12. PCES Which of the following always causes change in speed? A.balanced forces B.unbalanced forces C.either balanced or unbalanced forces D.any combination of forces

13. Problem: What type of force indicates a change in speed?

14. Claim:

15. Scientific Explanation: B When an object increases or decreases in speed, then the forces acting on the object are unbalanced.

16. Journal Entry – Case One A commentator has described an athlete as running northwest at 5 m/s. Which attribute of the athlete has the commentator described? A. force B. speed C. velocity D. acceleration

17. Problem: Which attribute of an athlete is described in running northwest at 5m/s.

18. Claim:

19. Scientific Explanation: Velocity = distance with direction time v = d with direction t v = d (meters) with direction t (seconds)

20. Journal Entry Case Two Acceleration is also described as the rate at which velocity changes. Based on the data table below, what is the acceleration of the ball in m/s2. Note: The unit for acceleration is m/s2.

21. Problem: What is the rate of change in velocity of the ball?

22. Claim:

23. Scientific Explanation: Rate of change in velocity is called acceleration. acceleration = change in velocity time = 19.6 m/s - 9.8 m/s = 9.8 m/s 2 s 2 s = 4.9 m/s2

24. Problem Solving

25. Speed, Velocity and Acceleration Problems

27. 1. A cat ran 50 meters north of the shopping center at a velocity of 6 m/s. How long did the cat run?

29. d 50 m s 6 m/s north t ?

30. velocity = 6m/s north distance = 50 m time = ? t = d = 50m = 8.33s s 6m/s

31. 2. Calculate the velocity of a car that went a distance of 135 kilometers north in 2 hours time.

33. d 135 km v ? m/s north t 2 hours

34. velocity = ? north distance = 135 kilometers time = 2 hours v= d =135 km t 2 h = 67.5 km/h north

35. 3. A ball is thrown a distance of 20 meters. What is its speed if it takes 0.4 seconds to cover the distance?

37. d 20 m s ? m/s t 0.4 s

38. speed = ? distance = 20 meters time = 0.5 seconds s = d = 20 m =50m = 50 m/s t 0.4 s s

39. 4. A car is travelling at a velocity of 500 km/h for 4 hours south of Arkansas. What is the total distance traveled?

41. d ? v 500 km/h south t 4 hours

42. velocity = 500 km/h distance = ? time = 4 hours d= v x t = 500km/h x 4 h = 2000 km

43. 5. What is the acceleration of a 50 kg object pushed with a force of 500 newtons?

44. 500N F 50kg m a a

45. F = a m 500 N= 500 kg. m/s2= 10m/s2 50kg 50kg

46. 6. If it takes Juan 4 seconds to run from the batters box to first base at an average speed of 6.8 m/s, what is the distance she covers in that time?

48. d ? s 6.8 m/s t 4 s

49. speed = 6.8m/s distance = ? time = 4 seconds d = s x t = 6.8m/s x 4s = 27.2 m

50. 7. A force of 250 N is applied to an object that accelerates at a rate of 5 m/s2. What is the mass of the object?