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Marking Period One Review

Marking Period One Review. v v v v. Which graph above best shows constant velocity motion?. e) none of them. t. t. t. t. a. b. c. d. Answer: b. Explanation: constant velocity means velocity does not change. Marking Period One Review.

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Marking Period One Review

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  1. Marking Period One Review v v v v Which graph above best shows constant velocity motion? e) none of them t t t t a b c d Answer: b Explanation: constant velocity means velocity does not change

  2. Marking Period One Review x x x x Which graph above best shows constant (non-zero) velocity motion? e) none of them t t t t a b c d Answer: a Explanation: constant velocity means position changes at a constant rate.

  3. Marking Period One Review a a a a Which graph above best shows constant velocity motion? e) none of them t t t t a b c d Explanation: constant velocity means zero acceleration, so none of these is correct Answer: e

  4. Marking Period One Review a a a a Which graph above best shows uniformly accelerated motion? e) none of them t t t t a b c d Answer: b Explanation: uniform acceleration means acceleration does not change.

  5. Marking Period One Review x x x x Which graph above best shows uniformly accelerated motion starting from rest? e) none of them t t t t a b c d Explanation: uniform acceleration from rest means increasing velocity starting from zero, which means increasing slope on a position vs. time graph. Answer: c

  6. Marking Period One Review v v v v Which graph above best shows uniformly accelerated motion from rest? e) none of them t t t t a b c d Answer: a Explanation: uniform acceleration means velocity is changing at a constant rate.

  7. Marking Period One Review v v v v A projectile is shot at an angle to the ground. It goes up and lands at its original level. Which graph above best shows the horizontal component of its velocity? e) none of them t t t t a b c d Answer: b Explanation: Horizontal velocity of a projectile is constant (ax = 0)

  8. Marking Period One Review v v v v A projectile is shot at an angle to the ground. It goes up and lands at its original level. Which graph above best shows the vertical component of its velocity? e) none of them t t t t a b c d Answer: a Explanation: Vertical velocity of a projectile shot at an angle starts positive, goes to zero (at the top of the arc) and then becomes negative on the way down.

  9. Marking Period One Review y y y y A projectile is shot at an angle to the ground. It goes up and lands at its original level. Which graph above best shows the vertical position vs. time? e) none of them t t t t a b c d Answer: d Explanation: Vertical position starts at zero (the ground) becomes positive, reaches a max, then goes back to zero.

  10. Marking Period One Review x x x x A projectile is shot at an angle to the ground. It goes up and lands at its original level. Which graph above best shows the horizontal position vs. time? e) none of them t t t t a b c d Answer: a Explanation: Horizontal velocity of a projectile is constant, so its horizontal position changes at a constant rate.

  11. Marking Period One Review • Velocity is: • A) the rate of change of acceleration • B) the rate of change of velocity • C) the rate of displacement • D) none of the above Answer: c Explanation: Velocity is rate of change of position. Displacement is change in position.

  12. Marking Period One Review • Acceleration is: • A) the rate of change of acceleration • B) the rate of change of velocity • C) the rate of change of position • D) the change in position • E) none of the above Answer: B Explanation: By definition.

  13. Marking Period One Review • Displacement is: • A) the rate of change of acceleration • B) the rate of change of velocity • C) the rate of change of position • D) the change in position • E) none of the above Answer: D Explanation: By definition

  14. Marking Period One Review A ball accelerates uniformly down an incline. It starts from rest and rolls 2 m in the first second. How far does it roll in the next second? a) 2 m b) 3 mc) 4 m d) 5 me) 6 m Explanation: The ball rolls 2 m in the first second, so its average velocity was 2 m/s during that second. It started with v = 0 m/s, so it ended the first second at 4 m/s (to make its average 2 m/s). If the ball went from 0 m/s to 4 m/s during the first second, it will go from 4 m/s to 8 m/s during the second second. If it goes from 4 m/s to 8 m/s, it will have an average velocity of 6 m/s, and will therefore travel 6 m during the second second. Answer: e

  15. Marking Period One Review What is the car’s velocity at t = 5 s? a) 2.5 m/s b) -2.5 m/sc) 5 m/sd) 1 m/se) 10 m/s Position (m) Answer: a Explanation: Velocity is slope of a position time graph. Slope of the section from 4 s to 6 s is (20 m/s – 15 m/s) / (6 s – 4 s) = 2.5 m/s

  16. Marking Period One Review What is the total distance traveled during the 12 seconds? a) 0 m b) -2.5 mc) 20 md) 40 me) 1.75 m Position (m) Answer: d Explanation: Distance is a scalar. The object went out 20 m then back 20 m for a total of 40 m.

  17. Marking Period One Review What is the acceleration at t = 8 seconds? a) -7.5 m/s2 b) 7.5 m/s2c) -1.5 m/s2d) 12.5 m/s2e) 0 m/s2 Position (m) Answer: e Explanation: Any straight section of a position vs. time graph represents constant velocity, and therefore a = 0.

  18. Marking Period One Review Velocity (m/s) What is the acceleration at t = 30 seconds? a) 25 m/s2 b) 0.5 m/s2c) -0.5 m/s2d) 0 m/s2e) 30 m/s2 Answer: b Explanation: Slope of velocity vs. time gives acceleration. Slope of that section is (30 m/s – 20 m/s) / (40 s – 20 s) = 0.5 m/s2

  19. Marking Period One Review Velocity (m/s) What is the displacement during the first 30 seconds? a) 525 m b) 600 m c) 25 m d) 750 me) 30 m Explanation: For each straight section, displacement equals average velocity times time. From 0 – 10 s: vave= (20+0)/2 = 10 m/s. 10 m/s*10s = 100m. From 10 – 20 s: vave = (20+20)/2 = 20 m/s. 20 m/s*10s = 200m. From 20 – 30 s: vave= (20+25)/2 = 22.5 m/s. 22.5 m/s*10s = 225m. Total = 100 m + 200 m + 225 m = 525 m. Answer: a

  20. Marking Period One Review 12 10 C 8 D A 6 x (m) At what two points is the velocity positive? a) A & B b) C & D c) B & E d) A & De) B & D B E 4 2 10 15 30 5 20 25 35 40 Time (s) Answer: a Explanation: On a position vs. time graph, slope of the tangent line equals velocity. Only points A & B have positively sloped tangent lines.

  21. Marking Period One Review 12 10 C 8 D A 6 x (m) At what two points is the acceleration positive? a) A & B b) C & D c) B & E d) A & De) B & D B E 4 2 10 15 30 5 20 25 35 40 Time (s) Answer: e Explanation: On a position vs. time graph, slope of the tangent line equals velocity. Acceleration is about change in velocity, so can be thought of as change in slope. Only at points B & D is the slope of the tangent line in the process of increasing. Increasing slope = increasing velocity = positive acceleration.

  22. A A C C Marking Period One Review Which vector below best shows the sum A + C? a) b) c) d) e) Answer: d Explanation:

  23. C Marking Period One Review Which vector below best shows A - C? a) b) c) d) e) Answer: a Explanation: A -C

  24. Marking Period One Review • Acceleration is: • A) the rate of change of acceleration • B) the rate of change of velocity • C) the rate of displacement • D) none of the above Explanation: By definition Answer: B

  25. Marking Period One Review • A projectile is shot on level ground at a 45o angle. If it has an initial vertical velocity of 30 m/s, how long will it be in the air? • A) 3 s • B) 6 s • C) 2.45 s • D) -6 s Answer: B Explanation: The vertical velocity decreases by 10 m/s every second (due to gravity) If it starts at 30 m/s it will take 3 seconds to get to zero. This is when it reaches its highest point. Over level ground it will take the same amount of time to come back down Total time in air is 6 seconds.

  26. Marking Period One Review • A projectile is shot on level ground at a 45o angle. If it has an initial vertical velocity of 30 m/s, how far will it travel horizontally? • A) 30 m • B) 60 m • C) 180 m • D) 360 m Answer: C Explanation: The total time in air is 6 seconds (see last slide for explanation). At 45o, the the horizontal velocity is the same as the initial vertical velocity, so it is also 30 m/s. ∆x = vxt, so ∆x = 30 m/s * 6 s = 180 m.

  27. Marking Period One Review • A projectile is shot on level ground at a 45o angle. If it has an initial vertical velocity of 30 m/s, how high does it go? • A) 30 m • B) 45 m • C) 60 m • D) 90 m Answer: B Explanation: The ball takes 3 seconds to reach the high point. The initial vertical on the way up is 30 m/s, the final vertical velocity (at the top) is 0 m/s. The average vertical velocity is therefore 15 m/s. 15 m/s * 3 s = 45 m.

  28. Marking Period One Review Vector A has a magnitude of 2, vector B has a magnitude of 8. Which is not a possible magnitude for the vector sum A+B? • A) 2 • B) 6 • C) 8 • D) 10 Answer: A Explanation: If the vectors are in the same direction they would add to a magnitude of 8+2 = 10. This is the maximum magnitude possible. If they are opposite, they will add to a magnitude of 8 – 2 = 6. This is the minimum magnitude possible.

  29. Marking Period One Review A boat can move at 4 m/s in still water. It heads east in a river which flows west at 3 m/s. What is the magnitude of its resultant velocity relative to the riverbank? • A) 5 m/s • B) 1 m/s • C) 7 m/s • D) none of these Answer: B Explanation: 4 m/s east + 3 m/s west = 1 m/s east.

  30. Marking Period One Review A boat can move at 4 m/s in still water. It heads east in a river which flows north at 3 m/s. What is the magnitude of its resultant velocity relative to the riverbank? • A) 5 m/s • B) 1 m/s • C) 7 m/s • D) none of these Answer: A Explanation: 4 m/s east + 3 m/s north (they are at right angles) = 5 m/s (C2 = A2 + B2)

  31. Marking Period One Review A car goes from 20 m/s to 80 m/s while traveling 1000 m. What was its average acceleration? • A) 3 m/s2 • B) 50 m/s2 • C) 5 m/s2 • D) 60,000 m/s2 Answer: A Explanation: You can use various kinematics equations here. One logical way: If speed goes from 20 m/s to 80 m/s average speed was 50 m/s. Going 1000 m at 50 m/s would take 20 s. So speed increased by 60 m/s in a time of 20 s, so acceleration was 60 m/s / 20 s = 3 m/s2.

  32. Marking Period One Review A car takes 10 seconds to drive around a circular track with a radius of 100 meters. What was the car’s average velocity for the one lap? • A) 0 m/s • B) 10 m/s • C) 10p m/s • D) 20p m/s Answer: A Explanation: Average velocity is total displacement over total time. Total displacement is zero, so average velocity is zero.

  33. Marking Period One Review A car takes 10 seconds to drive around a circular track with a radius of 100 meters. What was the car’s average speed for the one lap? • A) 0 m/s • B) 10 m/s • C) 10p m/s • D) 20p m/s Answer: D Explanation: Average speed is distance over time. Distance is circumference = 2πr = 200π. 200π / 10 s = 20π m/s

  34. Marking Period One Review Vector A = 30 m/s at 40o E of N. Which of the following is a proper expression for its component to the east? • A) 30 sin 40o • B) 30 cos 40o • C) 60 sin 40o • D) any of these Answer: A Explanation: Make a diagram Aeast A Sin Q = Aeast/A Aeast = ASin Q Q

  35. Marking Period One Review Several projectiles are launched on level ground at the same speeds, but at different angles (shown) above the horizontal. Once the projectiles land, rank the range of each from smallest to largest. 75o 60o 45o A) 15 < 30 < 45 < 60 < 75 B) 75 < 60 < 45 < 30 < 15 C) 15=75 < 30= 60 < 45 D) 15=60 < 30= 75 < 45 30o 15o Answer: C Explanation: On level ground 45o gives the greatest range and further from 45o means less range. Equal amounts from 45o (complimentary angles) have the same range.

  36. Marking Period One Review Several projectiles are launched on level ground at the same speeds, but at different angles (shown) above the horizontal. Once the projectiles land, rank the maximum height that each projectile reached from smallest to largest. 75o 60o 45o A) 15 < 30 < 45 < 60 < 75 B) 75 < 60 < 45 < 30 < 15 C) 15=75 < 30= 60 < 45 D) 15=60 < 30= 75 < 45 30o 15o Answer: A Explanation: For a given initial speed, max height is related to initial vertical velocity, which is biggest at bigger angles (Sin Q hits its maximum value at Q = 90o )

  37. Marking Period One Review Several projectiles are launched on level ground at the same speeds, but at different angles (shown) above the horizontal. Once the projectiles land, rank the time in air of each projectile from smallest to largest. 75o 60o 45o A) 15 < 30 < 45 < 60 < 75 B) 75 < 60 < 45 < 30 < 15 C) 15=75 < 30= 60 < 45 D) 15=60 < 30= 75 < 45 30o 15o Answer: A Explanation: For a given initial speed, time in air is related to initial vertical velocity, which is biggest at bigger angles (Sin Q hits its maximum value at Q = 90o )

  38. Shown in the eight figures below are toy trucks that are rolling along on tables. All of the trucks are identical. The tables they are on vary in height, and the speeds of the trucks vary. Specific values for the heights and speeds are given in the figures. Each truck rolls off the end of its table. Rank these trucks from shortest to longest, based on how long the trucks are in the air. That is, put first the truck that takes the least time to go from the edge of the table to the ground, and put last the truck that takes the most time.  Explanation: Time in air only depends on vertical velocity, not horizontal. All had 0 initial vertical velocity. So time depends only on initial height. Bigger height, more time. Answer: C A) F<H<E<A<D<G<B<C C) A=E=F < D=G=H < B=C B) B=H < C=D=F < E < A=G D) It depends on the mass of the cars

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