Q: If you choose upward as the positive $$y-$$direction, what is the correct value for the acceleration due to gravity in the kinematic equations?

$$a_y = -g = -9.80\,\text{m/s}^2$$

Question 1

Which equation correctly describes the final position $$x_f of an $$object undergoing constant acceleration $$a_x$$ over a time interval $$\Delta t$$, starting from initial position $$x_i$$ and initial velocity $$(v_x)_i$$?

Accepted Answer

$$x_f = x_i + (v_x)_i \Delta t + \frac{1}{2} a_x (\Delta t)^2$

Question 2

A car starts from rest and accelerates at $$2.0\,	ext{m/s}^2$$ for $$5.0\,	ext{s}. $$What is its final velocity?

Accepted Answer

$$10.0\,	ext{m/s}$$

Question 3

Which of the following statements about free fall is correct?

Accepted Answer

All objects fall with the same constant acceleration near Earth's surface if air resistance is negligible.

Question 4

A ball is thrown vertically upward with an initial velocity of $$8.0\,	ext{m/s}. $$What is the acceleration of the ball at its highest point?

Accepted Answer

$$-9.80\,	ext{m/s}^2$$

Question 5

If you choose upward as the positive $$y-$$direction, what is the correct value for the acceleration due to gravity in the kinematic equations?

Accepted Answer

$$a_y = -g = -9.80\,	ext{m/s}^2$$

Question 6

A stone is dropped from rest from a tall building. How far does it fall in the first $$2.0\,	ext{s}$$? (Neglect air resistance.)

Accepted Answer

$$19.6\,	ext{m}$$

Question 7

A jet starts from rest and accelerates at $$31\,	ext{m/s}^2$$ until it reaches a velocity of $$65\,	ext{m/s}. $$How far did it travel during this acceleration phase?

Accepted Answer

$$68.1\,	ext{m}$$

Question 8

Which equation is most useful for solving a constant acceleration problem when the time interval $$\Delta t is $$not given?

Accepted Answer

$$(v_x)_f^2$ = (v_x)_i^2$ + 2 a_x \Delta x$$

Question 9

A referee tosses a coin upward with an initial speed of $$5.00\,	ext{m/s}. $$What is the maximum height reached by the coin? (Neglect air resistance.)

Accepted Answer

$$1.28\,	ext{m}$$

Question 10

In the experiment shown in the second image, why do the rock and paper fall at the same rate in the evacuated tube?

Accepted Answer

There is no air friction, so both objects accelerate downward at $$g.$$

Question 11

A ball is thrown vertically upward from the edge of a $$50.0\,	ext{m}$$ cliff at $$15.0\,	ext{m/s}. $$How many seconds does it take for the ball to reach the bottom of the cliff? (Neglect air resistance.)

Accepted Answer

$$5.54\,	ext{s}$$

Question 12

Which physical quantity is represented by the area under the velocity vs. time graph shown in the first image?

Accepted Answer

Displacement $$\Delta x$$

Question 13

A boat has an initial velocity of $$6.0\,	ext{m/s}$$ and an acceleration of $$2.0\,	ext{m/s}^2. $$How far does it travel in $$8.0\,	ext{s}$$?

Accepted Answer

$$112\,	ext{m}$$

Question 14

If an object moves with constant velocity, which of the following statements is true?

Accepted Answer

Its acceleration is zero.

Question 15

A student drops a ball from a height of $$20\,	ext{m}. $$How long does it take to reach the ground? (Neglect air resistance.)

Accepted Answer

$$2.02\,	ext{s}$$

Question 16

Which step is NOT part of the recommended strategy for solving kinematics problems?

Accepted Answer

Plug in numbers immediately before solving algebraically.

Question 17

If the motion of an object is divided into segments with different acceleration values, what should you do when solving for its final position and velocity?

Accepted Answer

Use the final position and velocity of one segment as the initial values for the next segment.

1-D Kinematics III: Constant Acceleration and Free-Fall

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