A heavy stone of 8 kg is dropped into a lake, hitting the water with a speed of 7 m/s. Assuming we have a drag force of the bv with b = 120 kg/s, how long does it for the stone to reach 10% of its original speed? Please use g = 9.8 m/s^2.

Students design a model roller-coaster track. they place a rubber ball at the highest point on the track and let it go. the ball rolls along the track pulled only by the force of gravity. eventually, it comes to a stop. which change to the design will result in the ball moving the greatest distance?