Q: A driver with a reaction time of $$0.50\ \text{s}$$ and maximum deceleration of $$6.0\ \text{m/s}^2 is $$driving at $$20\ \text{m/s}$$ when she sees an obstacle $$50\ \text{m}$$ ahead. How much distance does she cover before stopping, and does she hit the obstacle?

She covers $$43\ \text{m}$$ and does NOT hit the obstacle.

Question 1

A car skids to a stop over a distance of 15.0 m in 0.750 s, slowing at a uniform rate of $$9.00\ 	ext{m/s}^2. $$What was the car's speed at the moment the brakes were first applied?

Accepted Answer

$$23.4\ 	ext{m/s}$$

Question 2

A driver with a reaction time of $$0.50\ 	ext{s}$$ and maximum deceleration of $$6.0\ 	ext{m/s}^2 is $$driving at $$20\ 	ext{m/s}$$ when she sees an obstacle $$50\ 	ext{m}$$ ahead. How much distance does she cover before stopping, and does she hit the obstacle?

Accepted Answer

She covers $$43\ 	ext{m}$$ and does NOT hit the obstacle.

Question 3

A train accelerates from rest at $$1.10\ 	ext{m/s}^2$$ for $$20.0\ 	ext{s}$$, travels $$1100.0\ 	ext{m} at $$constant speed, then decelerates at $$2.20\ 	ext{m/s}^2$$ until it stops. What is the total distance between stations?

Accepted Answer

$$1430\ 	ext{m}$$

Question 4

A ball is tossed straight up. After $$1.2\ 	ext{s}$$, it is falling downward at $$0.41\ 	ext{m/s}. $$What was its initial upward speed?

Accepted Answer

$$11.4\ 	ext{m/s}$$

Question 5

A stone is dropped from rest from the top of a tower and takes $$4.0\ 	ext{s} to $$reach the ground. How tall is the tower?

Accepted Answer

$$78\ 	ext{m}$$

Question 6

A ball is tossed straight downward from $$15.00\ 	ext{m}$$ and strikes the ground at $$30.0\ 	ext{m/s}. $$What was its initial speed?

Accepted Answer

$$24.6\ 	ext{m/s}$$

Question 7

An elevator descends at $$5.00\ 	ext{m/s}$$ for $$3.00\ 	ext{s}$$, then enters free-fall for $$1.50\ 	ext{s}. $$What is the total distance descended?

Accepted Answer

$$33.5\ 	ext{m}$$

Question 8

A puck slides toward a wall at $$8.00\ 	ext{m/s}$$, slowing at $$0.500\ 	ext{m/s}^2$$ and hits the wall after $$25.0\ 	ext{s}. $$What total distance did it slide?

Accepted Answer

$$43.75\ 	ext{m}$$

Question 9

A car decelerates uniformly from $$23.4\ 	ext{m/s} to$$ $$16.6\ 	ext{m/s}$$ over $$0.750\ 	ext{s}. $$What is the magnitude of its acceleration?

Accepted Answer

$$9.00\ 	ext{m/s}^2$$

Question 10

A train accelerates from rest at $$1.10\ 	ext{m/s}^2$$ for $$20.0\ 	ext{s}$$, then travels $$1100.0\ 	ext{m} at $$constant speed, and finally decelerates at $$2.20\ 	ext{m/s}^2$$ until it stops. What is the total time taken?

Accepted Answer

$$80\ 	ext{s}$$

Question 11

A ball is tossed straight downward from $$15.00\ 	ext{m}$$ and strikes the ground at $$30.0\ 	ext{m/s}. $$Which kinematic equation would you use to solve for the initial speed?

Accepted Answer

$$v^2$$ = $$v_0^2 + 2a$$\Delta y$$

Question 12

A stone is dropped from rest and falls $$78\ 	ext{m} in$$ $$4.0\ 	ext{s}. $$What is the value of $$g$$ used in this calculation?

Accepted Answer

$$9.8\ 	ext{m/s}^2$$

Question 13

A velocity-time graph shows an object moving in the negative direction with positive acceleration, passing the point where it changes direction. Which description best fits this motion?

Accepted Answer

The object slows down, stops, then speeds up in the positive direction.

Question 14

A ball is tossed upward and after $$1.2\ 	ext{s} is $$moving downward at $$0.41\ 	ext{m/s}. $$What is the total change in velocity during this time?

Accepted Answer

$$-11.81\ 	ext{m/s}$$

Question 15

A puck slows uniformly from $$8.00\ 	ext{m/s} to $$rest over $$25.0\ 	ext{s}. $$What is its acceleration?

Accepted Answer

$$-0.500\ 	ext{m/s}^2$$

Question 16

An elevator descends at $$5.00\ 	ext{m/s}$$ for $$3.00\ 	ext{s}$$, then enters free-fall for $$1.50\ 	ext{s}. $$What is its speed at the end of $$4.50\ 	ext{s}$$?

Accepted Answer

$$19.7\ 	ext{m/s}$$

Question 17

A car decelerates at $$9.00\ 	ext{m/s}^2$$ for $$0.750\ 	ext{s}$$, leaving skid marks $$15.0\ 	ext{m}$$ long. Which equation would you use to find the initial speed?

Accepted Answer

$$\Delta x = v_0$ t + \frac{1}{2} a t^2$

Question 18

A train accelerates from rest at $$1.10\ 	ext{m/s}^2$$ for $$20.0\ 	ext{s}. $$What is its speed at the end of the acceleration phase?

Accepted Answer

$$22.0\ 	ext{m/s}$$

Question 19

A stone is dropped from rest and falls for $$4.0\ 	ext{s}. $$Which equation would you use to find the height of the tower?

Accepted Answer

$$y = \frac{1}{2} g t^2$

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