21.A 100-g toy car is propellead by a comgnossod spring thut stus he final speed

Question

21.A 100-g toy car is propellead by a comgnossod spring thut stus he final speed of the toy car is 0.687 mis if its initial speed is 2.00 mis and its he frictionless slope, gining 0.180 m in altitade ap 22. (a) How long will it take an 850-kg car with a usefial power output of 40.0 hp (1 46 W) to reach a speed of 15.0m/s neglecting friction? (b) How long will this acceleration take if the car also climbs a 3.00-m-high hill in the process? 23. Two children are balanced on a seesaw with the center of mass of the seesaw 0 160m to the left of the pivot (on the side of the lighter child). The mass of the seesaw is 120kg while the mass of the lighter child is 26 kg and she sits 1.6 m from the pivot. The mass of the other child is 32 kg a. How far is the second child from the pivot? b What is the supporting force exerted by the pivot on the seesaw? 24. If you used an ideal pulley of the type shown in Part c of the figure below to support a engine of mass 115 kg, (a) What would be the tension in the rope? (b) What force must the ceiling supply, assuming you pull straight down on the rope assuming you pull straight up on the rope. The pulley system's mass is 7.00kg MA-2

Explanation / Answer

21)

vf^2 = vi^2 + 2gd

g = -9.8 m/s^2, d = 0.180 m,

vi = 2 m/s

mass is not needed.

vf^2 = 2^2 - (2 x 9.8 x 0.180)

vf^2 = 0.472 m^2/s^2

vf = 0.687 m/s

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