Honors Physics kinematics practice problems. – answers.

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14 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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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
  
    

 
 
 
 

    

  