Class Management | Help Chapter 10- Rigid body rotation Begin Date: 10/30 2017 1
ID: 1781129 • Letter: C
Question
Class Management | Help Chapter 10- Rigid body rotation Begin Date: 10/30 2017 11:00:00 AM Due Date: 11/12/2017 11:59:00 PM End Date: 11/12/2017 11:59:00 PM (1096) Problem 10: Consider the woman doing push-ups in the figure. She has a mass of 58.1 kg, and the distance from her feet to her center of mass is 0.84 m, while the distance from her feet to her hands is 1.6 m. CG Freaction Otheexpertta.com 25% Part (a) What force in newtons should the woman in the figure exert on the floor with each hand to do a push-up? Assume that she moves up at a constant speed. Grade Summary Deductions 0% Potentjal 100% tan() | |( 7 89 Submissions cotan asin atan acotan sinh( coshta cotanhO Attempts remaining: 6 (1 % per attempt) detailed view 0 Degrees O Radians SubrmitHnt I give up! Hints: 0% deduction per hint. Hints remaining: 3 Feedback: 1% deduction per feedback. 25% Part (b) The triceps muscle at the back of her upper arm has an effective lever arm of 1.75 cm. and she exerts force on the floor at a horizontal distance of 19.5 cm from the elbow joint. Calculate the magnitude of the force in newtons for each triceps muscle. 25% Part (c) How much work in joules does she do if her center of mass rises 0.15 m? 25% Part (d) what is her useful power output. in watts. if she does 25 pushups in one minute?Explanation / Answer
(A) constant speed means she is in equilibrium.
balancing moment about the feet point,
M = (a W) - (b 2 Fh) = 0
Fh = (0.84 x 58.1 x 9.81) / (2 x 1.6)
Fh = 149.6 N ........Ans
(B) (1.75 x Ft) - (19.5 x 149.6) = 0
Ft = 1667 N
(C) Work done = m g h = 58.1 x 9.81 x 0.15
= 85.5 J
(d) power =work done / time
= (25 x 85.5) / (1 x 60 s)
= 35.6 W