6. Intro to Forces (Dynamics)

Forces in 2D

Open Question
A man pushes on a piano with mass 180 kg; it slides at constant velocity down a ramp that is inclined at 19.0° above the horizontal floor. Neglect any friction acting on the piano. Calculate the magnitude of the force applied by the man if he pushes (a) parallel to the incline
Multiple Choice
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?
Multiple Choice
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?
Multiple Choice
A particle is acted upon by 3 forces: a $10 N$ force in the positive x direction, a $20 N$ force in the positive y direction, and an unknown force. If the particle is in equilibrium, what is the magnitude of the unknown force?
Multiple Choice
A $500 kg$ car is parked on a hill with a 5° slope. What is the magnitude of the friction force acting on the car?
Multiple Choice
A curve on an unbanked highway has a radius of 300 m. What minimum coefficient of static friction is required for a car to make the corner at $29 m / s$ (about $65 mph$ ).
Multiple Choice
A race track has turns of radius $400 m$ that are banked at 30° above the horizontal. What is the fastest a car could go around this corner with no assistance from friction?
Open Question
(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>
Open Question
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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Open Question
A man pushes on a piano with mass 180 kg; it slides at constant velocity down a ramp that is inclined at 19.0° above the horizontal floor. Neglect any friction acting on the piano. Calculate the magnitude of the force applied by the man if he pushes (b) parallel to the floor.
Open Question
An 85,000 kg stunt plane performs a loop-the-loop, flying in a 260-m-diameter vertical circle. At the point where the plane is flying straight down, its speed is 55 m/s and it is speeding up at a rate of 12 m/s per second. (b) What angle does the net force make with the horizontal? Let an angle above horizontal be positive and an angle below horizontal be negative.