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A 28-kg beginning roller skater is standing in front of a wall. By pushing against the wall, she is propelled backward with a final velocity of -1.2 m/s. While pushing, her hands are in contact with the wall for 0.80 s. Ignoring frictional effects, find the magnitude and direction of the average force on the skater.A force that varies with time is applied to an object. The force increases linearly from zero to 24 N during the first 3.0 seconds. Then, the force remains constant 4.0 seconds. During the last 2.0 seconds, the force linearly decreases to zero newtons. What is the total impulse exerted on the object? O This cannot be determined because the mass of the object is not given. O The total impulse is 186 N O The total impulse is 144 N O The total impulse is 156 N O The total impulse is 196 N.Ryan, m = 45 kg, runs and jumps off a stationary, 87-kg floating platform on a lake. Ryan's velocity as he leaps is +2.7 m/s. Ignoring any frictional effects, what is the recoil velocity of the platform