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B. Free fall - falling where the only force is gravity (no friction)

 

1. Free fall Word Problems

 

Use same method and
equations as before …

 

… except always remember
 when you read...

 

'…an object is dropped' 

 Vi = 0

 

a = g = +9.8m/s2
(make down +)

 


… an object is ascending:

a = g = -9.8 m/s2
(make down -)

 

 

 

 


a. Simple Freefall Problems

Leaning Tower of Pisa, in Pisa, Italy.

 (Wednesday 19 May 2004, 17:37) The lean of this tower has been tried to fix several times. The most recent time I believe was in 2001 when they tried to drill into the ground and pour cement underneath the sandy surface.

 

 

Ex) A coin is dropped in a vacuum tube, find its displacement after .30 seconds.

 

 
 Step 1 - Read and underline all the important information

 

 

 

 

Ex) A coin is dropped in a vacuum tube, find its displacement after .30 seconds.

 

Step 2 - Turn all your information into letters


 
 Vi = 0   (Object is dropped)
a = +10. m/s2
 d = ?
t = .30 seconds

Step 3 -  Substitute and Solve

 

 

 

d = Vit + 1/2at2 

 

 

d = 0m/s(.30 sec)+1/2(10. m/s2)(.30 s)2

 

 

 

 

 

d = 0 + 5(.09)

 

 

 

d = .45 m

 

 

 

 

 

 

 

Ex) Find the coin's velocity after
.30 seconds

 

Search the Mechanics Section on
the equation sheet to find the equation that fits

 

 

 

Ex) Find the coin's velocity after
.30 seconds

 

Vf = ?
t = .30 seconds
a = g = 9.8 m/s2 (falling)
Vi = 0 m/s

 

 

 

a = (Vf - Vi)/t

 

 

 

9.8 m/s2 = (Vf - 0 m/s)/.30 sec

 

 

 

 

Vf = 2.9 m/s

 

 

 

 

 

Ex) A rocket is fired vertically upward with an initial velocity of 29 m/s .

When the rocket reaches its maximum altitude it has a velocity
of 0 m/s. 

Find the rocket's maximum altitude.

 

 

 

 

Ex) A rocket is fired vertically upward with an initial velocity of 29 m/s . When the rocket reaches its maximum altitude it has a velocity of 0 m/s. 

 

Find the rocket's maximum altitude.

 

Altitude??

Vi = +29 m/s

Vf = 0 m/s
a = g = -9.8 m/s2

d = ?

 


 Vf2 = Vi2 + 2ad

(0 m/s)=(+29 m/s)2+2(-9.8m/s2)d


 

0 = 841 + -19.6d

 

 

-841 = -19.6d

 

 

43 m

 

 

 

 

Ex) An object dropped on planet X falls 64 m in 4 seconds. 
Find the acceleration due to gravity on planet X.

 

 

 

Ex) An object dropped on planet X falls 64 m in 4 seconds.  Find the acceleration due to gravity on
planet X.

 

 

Vi= 0 m/s
d = 64 m
t = 4 sec
a = ?

 

 

d = Vit + 1/2 at2

 

 

64 m = 0 m/s(4 sec) + 1/2a(4 sec)2

 

 

64 m = 0 + 8a

 

 

a = 8 m/s2

 

 

 

 

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