The football has 2 velocities.
Which velocity is the football player matching.

 

 

 

 

Horizontal velocity.
The football and the football player
have a constant horizontal velocity.

St. Mary's Show Me The Physics

 

 

Ex) A projectile leaves ground at an angle of 60.° and a speed of 100.m/s.

(a) Find the initial vertical component of the object's velocity

 

Ex) A projectile leaves ground at an angle of 60.° and a speed of  100. m/s.

 

(a) Find the initial vertical component of the object's velocity 

 

Ө = 60.°

 

Vi  = 100. m/s
Viy = ?

 

 

Viy = Vi(sinӨ)

 

 

= (100. m/s)sin60.°

 

 

 

 

Viy = 87. m/s up

 

 

 

 

 

(b) Find the objects maximum height.

 

Viy = 87. m/s
ay = -10 m/s2 (ascending)
dy (max) =?
Vfy = 0 (at max height)

 

 

Vf2 = Viy2 + 2ad

 

 

02 = (87. m/s)2 + 2(-10. m/s2)d

 

0 = 7569 + -20.dy

 

 

subtract 7569 from both sides

 

 

-7569 = -20.(dy)

 

 

dy = 378 m

 

 

Actually ......

 

 

 

dy = 380 m

 

 

(2 sig. figs)

 

 

 

ex) A rock is thrown from a cliff with initial speed of 40. m/s at an angle of 45.° below  the horizontal. 

(a) What is the vertical component of the initial velocity?

        

a) What is the vertical component  of the initial velocity?

Ө = 45.°

 
Vi = 40. m/s
Viy = ?     
 
Viy = VsinӨ
 
= (40. m/s)sin45.° 

			
 
Viy = 28 m/s down 

 

 

 

 

(b) If the rock strikes ground in 1 sec what is height of cliff?

 

 

 

 

(b) If the rock strikes ground in 1.0 sec what is height of cliff?

 

 

dy = ? (height)

ay = + 10. m/s2

 

t = 1.0 sec

 

Viy = 28 m/s (from before)

 

 

 

dy = Viyt + (˝)at2
 
 
 
 
 
= 28.m/s(1sec)+˝(10. m/s2)(1.0sec)2
 
 
 
28 m + 5.0 m
 

		
 
dy = 33 m down
 
 
 
 

 

At Peak,

 

 Vx = ?

 

 

 

Vx = 9.0 m/s

 

 

 

 

h

Total Time in Air?

 

 

 

1.84 sec
(twice peak)

 

 

actually 1.8

 

 

 

(2 sig. figs.)

 

 

 

 

 

What will the horizontal velocity of the baseball be just before it hits the ground?

 

 

 

 

9 m/s, Vx is constant

 


Monkey and Hunter
 Don Ion

(offsite)

 

 

 Flash Physics
 Don Ion

 

 

St. Mary's U. Astronomy and Physics Dept.

| Onsite |

 

 

 

 

 

 

 

 

 

 

Projectile Motion Game
St. Mary's Physics

 

 

 

 

 


 

 

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