iPad 12:32 AM * 70%-. session. Problem 9.40 MasteringPhysics A 50 kg sprinter, s

Question

iPad 12:32 AM * 70%-. session. Problem 9.40 MasteringPhysics A 50 kg sprinter, starting from rest, runs 54 m in 7.0 s at constant acceleration. Part A What is the magnitude of the horizontal force acting on the sprinter? Express your answer to two significant figures and include the appropriate units. F,= | Value Units Submit Request Answer Part B What is the sprinter's power output at 2.0 s,4.0 s, and 6.0 s? Express your answers using two significant figures separated by commas. P(20), P(4.0), P(6.0)= kW Request Answer

Explanation / Answer

a) applying second equation of motion to find acceleration

S= 0.5 at^2

54= 0.5*a*7^2

a= 2.204 m/s^2

now, foce is given by, F= ma= 50*2.204= 110.2 N

b) workdone by sprinter,

w= Fd= 110.2* d

power, P= w/t

AT t1= 2s, d= 0.5*2.204*2*2= 4.408 m

power P= w/t= 110.2*4.408/2= 0.2424 KW

at t2= 4 s

d= 0.5*2.204*4*4= 17.632 m

power, P= 110.2*17.632/4= 0.486 KW

at t3= 6 s

d= 0.5*2.204*6*6= 39.672 m

power, P= 110.2*39.672/6= 0.729 KW

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