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Student3.41

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## Homework Statement

To determine the mass of a car, a student (with a friend at the wheel) pushes the car holding a bathroom scale between himself and the car. The scale maintains a constant reading of 433 N while the car accelerates on level ground. At the conclusion of the experiement, his friend reports that the car accelerated from rest to 18.8 km/hr in 15.9 s. What was the mass of the car?

## Homework Equations

a= Delta V/Delta t

f=ma

w=mg

g=9.8m/s^2

## The Attempt at a Solution

a = 18.8km/hr/15.9s ------> 313m/s/15.9s = 19.7m/s^2 - > Acceleration of car.

F=ma, since the force is constant throughout the problem I assumed acceleration was constant.

W=mg ----> 422N=m(9.8m/s^2)--> m=43.06kg, is the weight.

f=ma ---> f=(43.1kg)(19.7m/s^2) = 847N

m= 847N/9.8m/s^2 = 86.4kg... incorrect.. am i doing too much ?