Select ItémS (c) it the object is initialy a rest, what is its speed ater 15.0s

Question

Select ItémS (c) it the object is initialy a rest, what is its speed ater 15.0s te) what are the velocity components of the object after 15.0 s7 (Let the velocity be denoted by w with your daughter in the snom. She sits on a sied and asks you to slide her across a fiat, horontal field.Y have a chaice of pushing her from behind by applying a foroe downward on her shouilders ac: 30* below the hontaontal (Pigure a) o attaching a rope to the front of the sled and puling with a force at 30° above the horiaontal (Figure b). Which wouild be easier for Tap to share with AirD

Explanation / Answer

1.

h=2.70t3, t=2.20s

h= 2.70*(2.20)^3 = 28.75 m

v=dh/dt = d/dt(2.70t3)= 3*2.70 t2 = 3*2.70*(2.20)^2 = 39.2 m/s

Now let us use kinematic eqn,

h= hf – hi = v*t-1/2*gt2

Final position is ground hence, hf =0m

Plug values,

0-28.75 = 39.2*t-1/2*9.8*t2

t= 8.7 s

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