Question

. A 9,100 kg tractor is moving (horizontally) at 5.0 km h−1 when the 80 kg driver has
to brake suddenly to come to a stop before hitting a tree stump. If the tractor and
driver come to rest over a horizontal distance of 2.0 m, and the acceleration of the
tractor and driver is constant, what is the magnitude of the net force on the driver

Answer 1

Initial velocity is $v_0=5.0 km/h= 1.389 m/s$

Final velocity is $v=0$

Distance traveled is $d=2.0 m$

The acceleration is

$a=\frac{v^2-v_0^2}{2d}=\frac{(0)^2-(1.389)^2}{2(2.0)}=-0.482 m/s^2$

the magnitude of the net force on the driver is

$F=ma=(80 kg)(0.482 m/s^2)=38.58 N=38.6 N$