# physics

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## Description

A bacterium moves with a speed of 2.3 Âµm/s across a petri dish with radius r = 9.2 cm. How long does it take the bacterium to traverse the petri dish along its diameter?

Speed=2.3 Âµm/s =2.3×10ʌ-6m/s

Radius=9.2cm =0.092m

Time =distance /speed

Time =0.092/2.3×10ʌ-6m/s=40000s =11.11 hours this is time taken by bacterium across a petri dish

Now time taken along the its diameter = 0.092×2/2.3×10ʌ-6m/s =80000s =22.22 hours

Sitting beside a friend on a park bench, you grab her hat and start running in a straight line away from her. Over the first 16.0 m, you accelerate at 1.5 m/s2 up to your maximum running speed. You then continue at your maximum running speed for 13.0 s more before your friend catches you. How far from the bench did you get before being caught? How long did it take for your friend to catch you?

Initial velocity =0m/s

Distance =16m

Acceleration =1.5m/s2

Time running at max speed =13s

Final velocity = 2×16×1.5=6.92m/s2

Time =?

Distance=initial distance + initial velocity× time +half× square time× acceleration

Distance=16+6.92×13+0.5×13×13×1.5 =232.7m

16m=0+0+ (0.5×t2×1.5)

16m=0.75t2

Time= (16/0.75)=4.6 s