Honors Physics kinematics practice problems.

–

answers.

Dr. Naumoff

1) A car accelerates from 5.0 m/s to 21 m/s at a rate of 3.0 m/s

2

. How far does it travel while

accelerating?

69 m

2 2

2 2

2

441 25

69.3

2 6

f i

f i

v v ad

v v

m

d

a s

2) An airplane needs to reach a velocity

of 203.0 km/h to take off. On a 2000 m runway, what is

the minimum acceleration necessary for the plane to take flight?

0.79 m/s

2

2

2 2

2 2

2

1000 1

203 56.4

1 3600

56.4

2 0.795

2 2 2000

f

f i

f i

km m h m

v

h km s s

m

v v

m

s

v v ad a

d m s

6) A car travels 95 km to the north at 70.0 km/h, then turns around and travels 21.9 km at

80.0

km/h. What is the difference between the average speed and the average velocity on this trip?

A)

27 km/h

1 2

95 21.9

1.36 0.274 t 1.36 0.274 1.634

70 80

tot

km km

t h t h h h h

km km

h h

tan 95 21.9 116.9

116.9

71.5

1.634

dis ce km km km

km km

average speed v

h h

95 21.9 73.1

73.1

44.7 North

1.634

displacement km km km

km km

average velocity v

h h

71.5 44.7 26.8

km km km

average speed average velocity

h h h

9) A car is

travelling north at 17.7 m/s. After 12 s its velocity is 14.1 m/s in the same direction.

Find the magnitude and direction of the car's average acceleration.

0.30 m/s

2

, South

2 2

14.1 17.7

0.3 or 0.3

12

f i

av

m m

v v

m m

s s

a South

t s s s

15) A dragster travels 1/4 mi in 6.7 s. Assuming

that acceleration is constant and the dragster is

initially at rest, what is its velocity when it crosses the finish line?

269 mi/h

0 d= 0.25mi t=6.7s

.25

0.0373 0.0373 3600 134.3

6.7

+ 0+

2 2 2

2

2 134.3 268.6

i

average

i f f f

average

average f

v

mi mi mi s mi

v

s s s h h

v v v v

v

v v

mi mi

h h

16) The average velocity of a car over a certain time interval is 37 mi/h. If the velocity of t

he car

was 65 mi/h at the end of this interval, what was its initial velocity? Assume that acceleration

was constant.

9 mi/h

65

37

2 2

2 37 65 9

i

i f

av

i

mi

v

v v

mi

h

v

h

mi mi mi

v

h h h

20) A toy rocket is launched vertically from ground level (y = 0 m), at time t = 0.0 s. The rocket

engine provides constant upward acceleration during the burn phase. At the instant of engine

b

urnout, the rocket has risen to

64 m and acquired a velocity of 60 m/s. The rocket continues to

rise in unpowered flight, reaches maximum height, and falls back t

o the ground. The time

interval, during which the rocket engine provides upward acceleration, is closest to:

2.1 s

2 2

2

2

2

2

2

64 60 0

2 0 2 2

2

60

a= 28.12

2 2 64

0

60

2.133

28.12

f i

f i

f

f

f i

f

f

m m

d m v v

s s

v v ad ad ad

v

a

d

m

v

m

s

d m s

v v at at at

v

t

a

m

v

s

t s

m

a

s

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