6. Intro to Forces (Dynamics)

Three horizontal forces act on a box (mass = 8 kg) sitting on a smooth surface. F₁ is 30 N acting at 53° counterclockwise from the +x axis, F₂ is 13 N acting at 67.4° clockwise from the +x axis, and F₃ is 20 N directly along the -x axis. What are the magnitude and direction of the box's acceleration?

You push a 5.1kg cart along the floor with an unknown force F at 30° below the horizontal. Using a scale, you know the Normal force is 70N. What is the horizontal acceleration of the cart?

(II) Two large snowcats are towing a housing unit north, as shown in Fig. 4–42. The sum of the forces F_A and F_B exerted on the unit by the horizontal cables is north, parallel to the line L, and F_A = 4200 N. Determine F_B and the magnitude of F→_A + F→_B . <IMAGE>

Andrea dangles her watch from a thin piece of string while the jetliner she is in accelerates for takeoff, which takes about 21 s. Estimate the takeoff speed of the aircraft if the string makes an angle of 24° with respect to the vertical, Fig. 4–61.

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