A person pushes a 8 kg crate 3m up a 29 degree incline with an 80 N force parall

Question

A person pushes a 8 kg crate 3m up a 29 degree incline with an 80 N force parallel to the incline. The fricitonal force is 17 N. Find the work done: a) by the person in Joules a) by gravity; in Joules a) by friction; in Joules

Explanation / Answer

(a) given h = 2.20 & ? = 20* =>By sin? = h/L =>Length of the slope (L) = h/sin? = 2.20/sin20* = 6.43 m =>By KE(final) + PE(final) = Work done =>KE(f) = Fcos? x L - mgh =>1/2mv^2 = 27 x cos20* x 6.43 - 5.3 x 9.8 x 2.2 =>1/2 x 5.3 x v^2 = 48.87 =>v = v18.44 =>v = 4.29 m/s (b)By F(net) = F(applied) - F(gravity) =>m x a = 27 x cos20* - mgsin20* =>5.3 x a = 25.37 - 5.3 x 9.8 x 0.34 =>a = 1.45 m/s^2 =>By v^2 = u^2 + 2as =>v^2 = 0 + 2 x 1.45 x 6.43 =>v = v18.65 =>v = 4.32 m/s

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