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Equilibrium Forces Physics Question?
A worker is poling a boat across a shallow lake. He pushes parallel to the length of the light pole, exerting on the bottom of the lake a force of 210 N. Assume the pole lies in the vertical plane containing the boat's keel. At one moment, the pole makes an angle of 25.0° with the vertical and the water exerts a horizontal drag force of 47.5 N on the boat, opposite to its forward velocity of magnitude 0.857 m/s. The mass of the boat including its cargo and the worker is 355 kg.
(a) The water exerts a buoyant force vertically upward on the boat. Find the magnitude of this force.
(b) Model the forces as constant over a short interval of time to find the velocity of the boat 0.350 s after the moment described.
1 Answer
- Anonymous1 decade agoFavorite Answer
a) Gravity force on boat = 355 . 9.8 = 3479 N
Total upward force = Buoyancy force + vertical component of the reaction to the push on the pole ( 210 . cos 25˚ )
Total upward force = Gravity force ( downwards)
Buoyancy force + 190.3 = 3479
Buoyancy force = 3288.7 = 3290 N ( to 3 sf)
b) Acceleration = F/m
Force = 210 . sin25˚ ( horizontal force from pole ) – 47.5
Forward force = 88.75 – 47.5 = 41.25 N
Acceleration = 41.25 / 355 = 0.116 m/s/s
V = U + (a . t)
V = 0.857 + ( 0.116 . 0.35 ) = 0.898 m/s
Source(s): Old teacher