6. The only two forcesacting on a body have magnitudes of 20 N and 35 N and dire

Question

6. The only two forcesacting on a body have magnitudes of 20 N and 35 N and directionsthat differ by 80°. The resulting acceleration hasa magnitude of 20 m/s2. What is the » mass of thebody?

7. A student lifts a boxof fresh roses, which just arrived from Mexico, 1.5 m in 3.0second. If she lifts the box the same distance in 6.0second, the work done by her is:A. thesame B. two times as great C. half asgreat D. one-fourth asgreat?

10. A 30-kg child rideson a circus Ferris wheel that takes her around a vertical circularpath with a radius of 20 m every 22 s. What is the magnitudeof the resultant force on the child at the highest point on thistrajectory?

13.           You have a machine that can accelerate pucks on frictionless ice.In time t the puck travels a distance x whenforce F is applied. If force 3F is applied,in time t, the distance the box travels?

17. When a certainrubber band is stretched a distance x,it exerts a restoring forceof magnitude F = Ax, where A is a constant whose value dependson the stiffness of the rubber band. The work done by a student instretching this rubber band from x = 0 to x = L is:

23. A hole Is drilled to thecenter of the Earth and a stone is dropped into it. When the stoneis at the Earth’s center, compared with the value at theEarth’s surface? A. its mass andweight are both changed B. its mass andweight are both zero C. its mass isunchanged and its weight is zero D. itsmass is unchanged and its weight approaches infinity its mass isunchanged and its weight isindeterminable.   

Explanation / Answer

(6) Given F = 20 N              F ' = 35 N Angle between two forces = 80 degrees resultant force F " = [ F ^ 2 + F ' ^ 2 + 2FF'cos ]                            = 43.22 N Accleration a = 20 m / s ^ 2 So, amss of the body m = F " / m                                      = 2.161 kg (7 ) work done W = mgh work done doesnot depend on time So, answer is same option ( A ) is correct

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