2.2.1 Describing Motion Under Constant Acceleration

Question 1

Describing Motion Under Constant Acceleration

Answer 1

• If acceleration is constant, the equations and completely describe one-dimensional motion.
• The equation is useful if you don’t have information about time intervals.

Question 2

note

Answer 2

• If acceleration is constant and you know the position and velocity of an object at an instant in time, these two equations allow you to predict the motion of the object at any point in time.
• Rearranging the definition for average acceleration and using the definition for results in the equation. Because we make the assumption of constant acceleration, average acceleration is the same as the acceleration at any point in time: . Substitution leads to the first master equation of kinematics: .
• Rearranging the definition for average velocity and using the definition for results in the equation .When acceleration is positive and constant, velocity increases linearly and . Substitution results in the equation. Using the first master equation of kinematics you can substitute for vf. The result is an equation for the final position of an object in terms of its initial position, initial velocity, acceleration and time. This is the second master equation of kinematics:.
• The final master equation of kinematics can be derived from the first two. It is most useful when you don’t have information about the change in time required for the motion of an object

Question 3

Assuming that average acceleration is constant, which of the following statements is correct?

Answer 3

None of the above.

Question 4

Which of the following does not show or describe constant acceleration?

Answer 4

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Question 5

Assuming constant acceleration, you can use the equation a = v/t to derive an equation for vc. Which of the following is used in this derivation?

Answer 5

rewrite v as vf-vi

Question 6

The plot shows velocity as a function of time. Assuming acceleration is constant and positive, which points correctly indicate vf, vi, and the average velocity?

Answer 6

vf = Point B; vi = Point A; v = Point D

Question 7

Which of the following statements about the master equations of kinematics with constant acceleration is not correct?

Answer 7

The master equations of kinematics assume that you know the change in time, Δt.

Question 8

Which of the following is the correct formula for vf  in terms of vi, a, and Δx ?

Answer 8

vf^2 = vi^2 + a(delta x)

Question 9

Which of the following statements about motion when there is constant acceleration is not correct?

Answer 9

xf = xi + vi delta t + 1/2a(delta t)^2