Question

24. A particle is on a smooth horizontal plane. A force graph is given. Then: F is applied w hose F vs t A) at t, the acceleration is constant B) initially body must be in rest C) at t, the acceleration is constant D) initially acceleration is zero E) Both C) and D) are correct. 25. A crate rests on a horizontal surface and a woman pulls on it with a 10 N force. Rank the situations shown below according to the magnitude of the normal force exerted by the surface on the crate, least to greatest. A) 1,2,3 B) 2, 1,3 C) 2,3, 1 D) 1,3,2 E) 3,2,1 10N 10N 10N 26. A forward horizontal force of 12 N is used to pull a 240 N crate at constant velocity across a horizontal floor. The coefficient of friction is: B) 0.05 C) 2 D) 0.2E) 20 A) 0.5

Answer 1

At t_2, the acceleration is constant, a_2 = F/m initially, force = 0, acceleration = 0 E) Both c and D are correct. N_2 = mg - 105 m theta N_3 = mg - 10 E) 3, 2, 1 f = kN = k(240) velocity = constant, acceleration = zero, f = 12 N rightwardsdoublearrow 12 = k (240) rightwardsdoublearrow k = 12/240 = 0.05 (B) 0.05