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.

		

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