Alternative Exercise 6.116 A block of ice with mass 6.10 kg is initially at rest

Question

Alternative Exercise 6.116 A block of ice with mass 6.10 kg is initially at rest on a frictionless, horizontal surface. A worker then applies a horizontal force F to it. As a result, the block moves along the x-axis such that its position as a function of time is given by a(t) at 2 +Bt3, where a 0.210 m/s and B 1.99x10-2 m/s previous l 12 of 15 l next Part B Calculate the magnitude of Fat time t 4.50 s Express your answer to three significant figures. F 5.84 N Submit My Answers Give Up Correct Part C Calculate the work done by the force F during the first time interval of 4.50 sof the motion. Express your answer to three significant figures. W 35.425 Submit My Answers Give Up incorrect; Try Again; 3 attempts remaining Provide Feedback Continue

Explanation / Answer

velocity is the derivative of displacement
x’(t)= 0.21t + 1.99x10^-2t²
x’(4.5)= 1.35

v=1.35m/s

As the mass started at rest and there is no friction, the Work over the interval will equal the kinetic energy of the mass at time = 4.5 seconds.
W = KE = ½mv²
W = ½6.10(1.35)²
W = 5.56 J <===ANSWER

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