Object Thrown Horizontally

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How many velocities?

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2 velocities

Horizontal velocity - Determined by thrower

 

Vertical velocity - ??????

 

 

acceleration due to gravity

 

 

 

 

 

b. Objects propelled horizontally

 

- have 2 velocities Vx, Vy

- Vx is determined by thrower

 

- Vx  constant  (neglect fricition)

 

- Viy = 0 (initial vert. vel.)

 

- Vy changed by ........

 

force of gravity

 

 

Ex) Object thrown horizontally a velocity of 4 m/s

time
(sec)
Vx
(m/s)
Vy
(m/s)
0 4 0
1 4 10
2 4 20
3 4 30

 

Object dropped/Objects thrown horizontally

Same:

a) ay  (+10 m/s2 )

b) vertical drop -  dy

c) time in air

d) same Vy

 

 

Compare each sphere's:

A) height above the ground,

B) time in the air

| Flash |
St. Mary's Physics Online

 

 

 

Compare the time it takes for the marbles to hit the ground.

 

 

 

Dropped/Projected Horizontally
Rutgers U

 

 

[ Flash ]
St. Mary's Physics Online

 

 

 

 

 

 

 

 

 

object projected horizontally

 

 

 

 

 

Ex1) A rock is thrown horizontally from the top of a cliff @ 150 m/s. 

a) How long does it take the rock to fall 45 m vertically.

 

 

 

 

Step 1 - Underline

 

Ex1) A rock is thrown horizontally from the top of a cliff @ 150 m/s

a) How long does it take the rock to fall 45 m vertically.

 

 

 

 

 

Step 2 - Turn information into letters

(Don't mix y information with x information)


Horizontal Vertical
Vx = 150 m/s Viy = 0
(thrown horizontally)
t = ? ay=+9.8 m/s2
  dy = 45 m
  t = ?

 

 

 

 

 

 

Step 3 -  Substitute and Solve

 

 

 

∆dy = Viyt + 1/2ayt2

 

 

 

45 m = 0 + ˝(9.8 m/s2)t2

 

 

 

45 m = 4.9t2

 

 

 

 

9 = t2


 

t = 3 seconds

 

 

 

 

 

 

A rock is thrown horizontally from the top of a cliff @ 150 m/s

b) Find the rock's vertical velocity at 45 meters

 

Horizontal Info Vertical Info
Vx = 150 m/s Viy = 0
(thrown horizontally)
  ay=+9.8 m/s2
  dy = 45 m
  Vfy = ?

 

 

 

 

 

 

 

Vfy2 = Viy+ 2ad

 

 

Vfy2 = 0+ 2(+9.8 m/s2)45m

Vfy2 = 19.6(45)

 

 

Vfy = 30 m/s

 

 

 

 

 

Only X Equation

** dx = Vxt **

(from Vx = dx/t)

 




dx - Horizontal distance
Vx - horizontal velocity

 

 

 

 

ORIGINAL QUESTION

Ex1) A rock is thrown horizontally from the top of a cliff @ 150m/sHow long does it take the rock to fall 45 m vertically

 

c) What was the rocks' horizontal displacement after 3.0 seconds?

 

 

Horizontal Vertical
Vx = 150 m/s Viy = 0
(thrown horizontally)
t = 3.0 sec ay = 9.8 m/s2
dx = ? dy = 45 m
  t = 3.0 sec

 

Given

 

Vx = 150 m/s 

(Object thrown horizontally) 

 

dx = ?

(A.K.A. Range)

 

t = 3.0 seconds

 

 

 

 

 

** dx  = Vxt **

 

 

dx = 150 m/s(3.0 seconds)

 

 

 

= 450 m

 

 

 

 

 


 

 

 

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