physics
posted by ashley on .
you find it takes 200N of horizontal force to move an empty pickup truck along a level road at a speed of 2.4m/s. you then load the pickup truck and pump its tires so that its total weight increases by 42% while the coefficient of rolling friction decreases by 19%. now what horizontal force will you need to move the pickup along the same road at the same speed? the speed is low enough that you can ignore air resistance.

original friction= 200N
reduce by .19%: 162N
weight increased by 42%, increases friction by 1.42
new horizontal force: 200*.81*1.41 
i don't quite understand how you reduced 200N to 162N ?

81% of 200 N is 162 N, the new rolling friction force if the weight stayed the same. You must also account for the higher weight.
The 1.41 in Mr. Pursley's final formula should be 1.42 
thank you so much this really helps :)