# Velocity and M/s

B) 45 km/h

C) 48 km/h

D) 53 km/h

E) 80 km/h

30’+60’ = 90’=5400s=1.5h

40km+40km=80km

vavg= 80000m/5400s=13.168724279835390946502057613169 m/s = 48 km/h

2. The coordinate of an object is given as a function of time by x = 7t – 3t2, where x is in meters and t is in seconds. Its average velocity over the interval from t = 0 to t = 2 s is: A) 5 m/s

B) –5 m/s

C) 11 m/s

D) –11 m/s

E) –14.5 m/s

vt= 7-6t = 7-12=-5 m/s

3. The coordinate of a particle in meters is given by x(t) = 16t – 3.0t3, where the time t is in seconds. The particle is momentarily at rest at t = A) 0.75 s

B) 1.3 s

C) 5.3 s

D) 7.3 s

E) 9.3 s

0=16-9t2

t2=16/9

t=1.33 s

4. Over a short interval near time t = 0 the coordinate of an automobile in meters is given by x(t) = 27t – 4.0t3, where t is in seconds. At the end of 1.0 s the acceleration of the auto is: A) 27 m/s2

B) 4.0 m/s2

C) –4.0 m/s2

D) –12 m/s2

E) –24 m/s2

at= -24t

5. Each of four particles move along an x axis. Their coordinates (in meters) as functions of time (in seconds) are given by | particle 1: x(t) = 3.5 – 2.7t3|

| particle 2: x(t) = 3.5 + 2.7t3|

| particle 3: x(t) = 3.5 + 2.7t2|

| particle 4: x(t) = 3.5 – 3.4t – 2.7t2|

Which of these particles is speeding up for t> 0?

A) All four

B) Only 1

C) Only 2 and 3

D) Only 2, 3, and 4

E) None of them

6. A car moving with an initial velocity of 25 m/s north has a constant acceleration of 3 m/s2 south. After 6 seconds its velocity will be: A) 7 m/s north

B) 7 m/s south

C) 43 m/s north

D) 20 m/s north

E) 20 m/s south

v = v0 + at = 25+3x6= 43m/s

7. A particle goes from x = –2 m, y = 3 m, z = 1 m to x = 3 m, y = –1 m, z = 4 m. Its displacement is: A)

B)

C)

D)

E)

8. A...

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