A world-class sprinter accelerates to his maximum speed in 4.2s . He then maintains this speed for the remainder of a 100-m race, finishing with a total time of 9.3s .

 

 

What is the runner's average acceleration during the first 4.2 ?

 

What is his average acceleration during the last 5.1 ?

 

What is his average acceleration for the entire race?

 

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An alert hiker sees a boulder fall from the top of a distant cliff and notes that it takes 1.30s for the boulder to fall the last third of the way to the ground. You may ignore air resistance.

 

What is the height of the cliff in meters?

 

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A marble is released from one rim of a hemispherical bowl of diameter 55.0cm and rolls down and up to the opposite rim in 10.0s .

 

 

Find the average speed.

 

Find the average velocity of the marble.

There are 4 equations of motion which allow you to solve any of these problems.

Look up 'the equations of motion' on the internet:

 

s= ut + 1/2 at^2

v = u + at

v^2 = u^2 - 2as

s = 1/2(u+v)t

 

where:

u = initial velocity (at t = o)

v = velocity at time t

t = time

s = distance

a = accelaration.

 

 

Use these and some logic to solve your problems.