# Question #39b14

##### 1 Answer

(a) Given street incline

Let Distance moved by Chemistro along the street

Total energy of Chemistro at any instant of time

#=mgh+1/2mv^2#

Where#m# is mass of Chemistro and#g=10ms^-2# acceleration due to gravity

Initial total energy

Initial kinetic energy gets converted in

Final total energy when he comes to rest

Now work done by friction

From the figure we see that the normal reaction

#N = mgcos20^@#

therefore force of the sliding friction is

#F_f= μ_kN = μ_kmgcos20^@#

#:.W=-μ_kmgcos20^@xxl#

As force of friction and distance moved are opposite to each other we have#-ve# sign.

Inserting given values and using law of conservation of energy we get

#21780=900lsin 20^@+0.333xx90.0xx10lcos20^@#

#=>21780=900lxx0.3420+0.333xx90.0xx10lxx0.9397#

#=>21780=(307.8+281.6)l#

#=>l=37.0m# , three significant figures

#:.h=36.95xxsin20^@#

#=>h=12.6m#

(b) Heat generated by sliding is same as work done against friction

#=0.333xx90.0xx10xxlcos20^@#

#=0.333xx90.0xx10xx36.95xx0.9397=10406J#

(c) We know that power is the rate of doing work per unit time.

#:.# Average power delivered by Power Man#=21780/0.300# #=72600Js^-1#