A new planet is discovered that has twice the Earth\'s mass and twice the Earth\

Question

A new planet is discovered that has twice the Earth's mass and twice the Earth's radius. On the surface of this new planet, a person who weights 500 N on Earth would experience a gravitational force of a. 125 N b. 250 N c. 500 N d. 1000 N e. 2000 The graph above represents position x versus time 1 for an object being acted on by a constant force. The average speed during the interval between 1 s and 2 s is most nearly a. 2 m/s b. 4 m/s c. 5 m/s d. 6 m/s e. 8 m/s The diagram below refers to questions 25 and 26. A student obtains data on the magnitude of force applied to an object as a function of time and displays the data on the graph above. The slope of the "best fit" straight line is most nearly a. 5 N/s b. 6 N/s c. N/s d. 8 N/s e. 10 N/s The increase in the momentum of the object between t = 0 s and t = 4 s is most nearly a. 40 N-s b. 50 N-s c. 60 N-s d. 80 N-s e. 100 N-s How does an air mattress protect a stunt person landing on the ground after a stunt? a. It reduces the kinetic energy loss of the stunt person. b. It reduces the momentum change of the stunt person. c. It increases the momentum change of the stunt person. d. It shortens the stopping time of the stunt person and increases the force applied during the landing. e. It lengthens the stopping time of the stunt person and reduces the force applied during the landing.

Explanation / Answer

23) Acceleration due to gravity on earth, g = GM/R^2 [ M is mass of earth, R is radius of earth]
acceleration due to gravity on new planet = g' = G(2M)/4R^2 = g/2
so, weight on earth = 500 N
weight on new planet = 250 N
Option b
24) Average speed = diplacement/time = (8 - 2)/1 = 6m/s
option d
25) slope = (10-5)/1 = 5 N/s
option a.
26) change in momentum = force*time
change in momentum = area under curve = 4*5 + 0.5*4*20 = 20 + 40 = 60 Ns
option c.
27) the answer is
e. it lengthens the stopping time, and as the change in momentum is constant, it effectly reduces the force experienced by the athlete

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