Aparachutist whose mass is 65 kg drops from a helicopter hovering 2500 m above the ground and falls toward the ground under the influence of gravity. assume that the force due to air resistance is proportional to the velocity of the parachutist, with the proportionality constant b 1equals20 n-sec/m when the chute is closed and b 2equals90 n-sec/m when the chute is open. if the chute does not open until the velocity of the parachutist reaches 25 m/sec, after how many seconds will the parachutist reach the ground? assume that the acceleration due to gravity is 9.81 m divided by sec squared.

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

A250-n box is at rest on a frictionless horizotal floor. then a person shoves the box with a non-zero force of magnitude p. which statement best describes the relationship betweeen p and the motion of the box after it was shoved? -the box will not move when p< 250n but otherwise will accelerate at a constant rate that is directly proportional to p - the box will begin moving at a speed that is directly proportional to p, then will gradually slow to a halt -the box will move with constant velocity at a speed that is directly proportional to p -box will accelerate across the floor at a constant rate that is directly proportional to p

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?