Name_** Answers**_

Acceleration BookWork Section 2-2 (odds academic, all honors.. check book for answers!)

D=Vavg*T Vavg= (Vi+Vf)/2 A= (Vf-Vi)/T

Pg 49

1) When the shuttle bus comes to a sudden stop to avoid hitting the dog, it slows from 9 m/s to 0 m/s in 1.5 s. Find the average acceleration of the bus.

*Vi= 9 m/s, Vf= 0 m/s, T= 1.5 sec, A= ??*

* A = (0-9)/1.5 = -6 m/s*^{2 }

2) A car traveling initially at 7 m/s accelerates to a velocity of 12 m/s in 2 s. What is the average acceleration of the car?

*Vi= 7 m/s, Vf = 12 m/s, T = 2 sec, A=??*

*A = (12-7)/2 = 2.5 m/s*^{2 }

3) Turner’s treadmill starts with a velocity of -1.2 m/s and speeds up at regular intervals during a half hour workout. After 25 min, the treadmill has a velocity of -6.5 m/s . What is the average acceleration of the treadmill during this period?

*Vi= -1.2 m/s, vf = -6.5 m/s, T = 25 min = 25*60=1500
sec!A=??*

*A = ( -6.5 - -1.2)/1500 =
-.004 m/s*^{2 }

4) If a treadmill starts at a velocity of -2.7 m/s and has a velocity of -1.3 m/s after 5 min, what is the average acceleration of the treadmill?

*Vi= -2.7 m/s, vf = -1.4 m/s, T = 5 min = 5*60=300
sec!, A= ??*

*A = ( -1.3 - -2.7)/300 = .005 m/s*^{2}

5) With an average acceleration of -0.5 m/s^{2} ,
how long will it take a cyclist to bring a bicycle with an initial velocity of
13.5 m/s to a complete stop?

*A= -0.5 m/s ^{2}*

*-.5 = (0-13.5)/T *

*-.5*T=-13.5*

*T= -13.5/-.5*

*T= 27 sec*

Name__** Answers**__

Acceleration BookWork Section 2-2 (odds academic, all honors.. check book for answers!)

D=Vavg*T Vavg= (Vi+Vf)/2 A= (Vf-Vi)/T

Pg 53

1) A car accelerates uniformly from rest to a speed of 23.7 km/hr in 6.5 sec. Find the distance the car travels during this time.

*Vi=0, Vf = 23.7km/hr = 23700m/3600sec =6.583 m/s,
T=6.5 sec, D=???*

* *

*D= (Vi+Vf)/2 *T D=
(6.583+0)/2 *(6.5) D= 3.29 * 6.5 = 21.4 m*

2) When Maggie applies the brakes of her car, the car slows uniformly from 15 m/s to 0 m/s in 2.5 sec. How many meters before a stop sign must she apply her brakes in order to stop at the sign?

*Vi=15 m/s, Vf = 0 m/s, T = 2.5 sec, D = ???*

* *

*D=(Vi+Vf)/2 *T D=
(15+0)/2 * (2.5) D = 7.5 * 2.5 = 18.75 m*

3) A jet plane lands with a velocity of 100 m/s and can accelerate at a maximum rate

of -5.0 m/s^{2
} as it comes to rest. Can this plane land at an airport where the runway
is 0.8 km long?

* Vi = 100,
Vf = 0, A =-5.0 m/s ^{2 }*

* *

*A=
(Vf-Vi)/T first*

*-5 =(
0-100)/T T=
-100/-5 = 20 seconds*

* *

*D=(Vi+Vf)/2
*T D= (0+100)/2 *
(20) D = 50 * 20 = 1000 m or 1.0 km NO!!*

4) A driver in a car traveling at a speed of 78 km/hr sees a cat 100 m away on the road. How long will it take for the car to accelerate constantly to a stop in exactly 99 m?

*Vi= 78
km/hr = 78000m/3600sec=21.67 m/s, Vf = 0, D=99m, T =???*

* *

*D=(Vi+Vf)/2
*T 99= (21.67+0)/2
* (T)*

*99=10.83
* T T=99/10.83
= 9.14 sec*

5) A car enters the freeway with a speed of 23 km/hr and accelerates to a speed of 86 km/hr in 3.5 min. How far does the car move while accelerating?

*Vi= 23
km/hr = 23000m/3600 sec = 6.389 m/s, Vf = 86 km/hr = 86000/3600 = 23.89 m/s*

*T= 3.5 min=
3.5*60=210 sec, D =???*

*D=(Vi+Vf)/2
*T *

* *

*D=
(6.389+23.89)/2 * (210) D = 15.14 * 210 = 3179 m or 3.18 km*

* *