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## You will never be confident that you know what you’re doing .

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**You will never be confident that you know what you’re**doing. • You must try in spite of the fact that you don’t know what you’re doing. • You will fail. • You must try again. Failure is a requirement; don’t fear it. • If you keep stepping up and trying, greatness is guaranteed. • You will be a leader in whatever field you choose to apply yourself. Your life will be bold, unique, worthwhile, and admired. • Right now you are the next Newton, Einstein, Feynman. • All you need to do is try things when you don’t know what you’re doing.**A person initially at point P in the illustration stays**there a moment and then moves along the axis to Q and stays there a moment. She then runs quickly to R, stays there a moment, and then strolls slowly back to P. Which of the position vs. time graphs below correctly represents this motion? C A B D F E**A person initially at point P in the illustration stays**there a moment and then moves along the axis to Q and stays there a moment. She then runs quickly to R, stays there a moment, and then strolls slowly back to Q. Which of the position vs. time graphs below correctly represents this motion? C A B D F E**The graph shows position as a function of time for two**trains running on parallel tracks. Which is true? A. At time tB, both trains have the same velocity. B. Both trains speed up all the time. C. Both trains have the same velocity at some time before tB. D. Somewhere on the graph, both trains have the same acceleration.**The graph shows position as a function of time for two**trains running on parallel tracks. Which is true? A. At time tB, both trains have the same velocity. B. Both trains speed up all the time. C. Both trains have the same velocity at some time before tB. D. Somewhere on the graph, both trains have the same acceleration.**Velocity is ….?**Acceleration is…? The slope of a secant line in the velocity vs time curve is… The slope of a tangent line in the velocity vs time curve is… The slope of a secant line in the position vs time curve is… The slope of a tangent line in the position vs time curve is…**A train car moves along a long straight track. The graph**shows the position as a function of time for this train. The graph shows that the train: A. speeds up all the time. B. slows down all the time. C. speeds up part of the time and slows down part of the time. D. moves at a constant velocity.**A train car moves along a long straight track. The graph**shows the position as a function of time for this train. The graph shows that the train: A. speeds up all the time. B. slows down all the time. C. speeds up part of the time and slows down part of the time. D. moves at a constant velocity.**A marathon runner runs at a steady 15 km/hr. When the runner**is 7.5 km from the finish, a bird begins flying from the runner to the finish at 30 km/hr. When the bird reaches the finish line, it turns around and flies back to the runner, and then turns around again, repeating the back-and-forth trips until the runner reaches the finish line. How many kilometers does the bird travel? A. 10 km B. 15 km C. 20 km D. 30 km**A marathon runner runs at a steady 15 km/hr. When the runner**is 7.5 km from the finish, a bird begins flying from the runner to the finish at 30 km/hr. When the bird reaches the finish line, it turns around and flies back to the runner, and then turns around again, repeating the back-and-forth trips until the runner reaches the finish line. How many kilometers does the bird travel? A. 10 km B. 15 km C. 20 km D. 30 km**You are throwing a ball straight up in the air.**At the highest point, the ball’s A. velocity and acceleration are zero. B. velocity is nonzero but its acceleration is zero. C. acceleration is nonzero, but its velocity is zero. D. velocity and acceleration are both nonzero.**You are throwing a ball straight up in the air.**At the highest point, the ball’s A. velocity and acceleration are zero. B. velocity is nonzero but its acceleration is zero. C. acceleration is nonzero, but its velocity is zero. D. velocity and acceleration are both nonzero.**Acceleration**If the velocity of a car is non-zero, can the acceleration of the car be zero? A) yes B) no C) depends on the velocity**Acceleration**If the velocity of a car is non-zero, can the acceleration of the car be zero? A) yes B) no C) depends on the velocity**Acceleration**If the acceleration of a car is non-zero, can the velocity of the car be zero? A) yes B) no C) depends on the acceleration**Acceleration**If the acceleration of a car is non-zero, can the velocity of the car be zero? A) yes B) no C) depends on the acceleration**If you drop an object in the absence of air resistance, it**accelerates downward at 9.8 m/s2. If instead you throw it downward, its downward acceleration magnitude after release is A. less than 9.8 m/s2. B. 9.8 m/s2. C. more than 9.8 m/s2.**If you drop an object in the absence of air resistance, it**accelerates downward at 9.8 m/s2. If instead you throw it downward, its downward acceleration magnitude after release is A. less than 9.8 m/s2. B. 9.8 m/s2. C. more than 9.8 m/s2.**A person standing at the edge of a cliff throws one ball**straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed is the one initially thrown A. upward. B. downward. C. neither—they both hit at the same speed.**A person standing at the edge of a cliff throws one ball**straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater speed is the one initially thrown A. upward. B. downward. C. neither—they both hit at the same speed.**A cart on a roller-coaster rolls down the track shown below.**As the cart rolls beyond the point shown, what happens to its speed and acceleration in the direction of motion? A. Both decrease. B. The speed decreases, but the acceleration increases. C. Both remain constant. D. The speed increases, but acceleration decreases. E. Both increase. F. Other**A cart on a roller-coaster rolls down the track shown below.**As the cart rolls beyond the point shown, what happens to its speed and acceleration in the direction of motion? A. Both decrease. B. The speed decreases, but the acceleration increases. C. Both remain constant. D. The speed increases, but acceleration decreases. E. Both increase. F. Other