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ra1l [238]
4 years ago
7

A strong-armed physics student throws a tennis ball vertically. The ball stays in the air for 5.5 seconds. Assuming the ball lef

t from the ground, how fast did it leave his hand?
Physics
1 answer:
Mila [183]4 years ago
4 0

Answer:

27.5 m/s

Explanation:

applying motion equations we can find the answer,

v = u + a*t

Let assume ,

u = starting speed(velocity)

v = Final speed (velocity)

t =  time taken for the motion

a = acceleration

by the time of reaching the highest point subjected to the gravity , the speed should be equal to zero  (only a vertical speed component is there)

for the complete motion it takes 5.5 s. that means to reach the highest point it will take 5.5/2 =2.75 seconds

we consider the motion upwards , in this case the gravitational  acceleration should be negative in upwards (assume g=10 m/s2)

that is,

v = 0 , a = -10ms^{-2}    , t =2.75

v = u + at

0 = u -10*2.75

u = 27.5 ms^{-1}

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I notice the wheels on my bicycle spin in a circular motion as I am pedaling. I know that the
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You stand on a straight desert road at night and observe a vehicle approaching. This vehicle is equipped with two small headligh
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Complete Question

You stand on a straight desert road at night and observe a vehicle approaching. This vehicle is equipped with two small headlights that are 0.681 m apart. At what distance, in kilometres, are you marginally able to discern that there are two headlights rather than a single light source?Take the wavelength of the light to be 549 nm and your pupil diameter as 4.63 mm.  

Answer:

The distance is  z  = 4707.6 \ m

Explanation:

From the question we are told that

    The is distance between the headlight is d = 0.681 \ m

   The wavelength is  \lambda = 549 \ nm = 549 *10^{-9} \ m

    The  pupil diameter is  D  = 4.63 \ mm = 0.00463 \ m

Generally, we can mathematically evaluate the resolution of the eye as

            \theta  = \frac{1.22 *  \lambda }{D}

    substituting values

              \theta  = \frac{1.22 *  549 *10^{-9} }{0.00463}

              \theta  =  (1.45 *10^{-4} )^o

Now according to SOHCAHTOA rule  

         sin \theta  =  \frac{ d}{z}

Where z is  the distance at which the eye can discern the two head light

  given that the angle is very small sin \theta =  \theta

=>    \theta  =  \frac{ d}{z}

substituting values

     1.45*10^{-4}  =  \frac{ 0.681}{z}

=>   z  = \frac{0.681}{1.45 *10^{-4}}

=>    z  = 4707.6 \ m

   

6 0
4 years ago
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