Akid is on a stationary sled, on snowy ground with us=0.125. it takes 71.2n of force to get the sled moving. how much normal force is acting?

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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b.transmitters send radio waves, and receivers capture radio waves.

no. dot product   =0 when vecs at right angles

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.