Question
16. A driver of a 7.50 x 103 N car passes a sign stating
“Bridge Out 30 Meters Ahead.” She slams on the brakes,
coming to a stop in 10.0 s. How much work must be done
by the brakes on the car if it is to stop just in time? Neglect
the weight of the driver, and assume that the negative
acceleration of the car caused by the braking is constant
“Bridge Out 30 Meters Ahead.” She slams on the brakes,
coming to a stop in 10.0 s. How much work must be done
by the brakes on the car if it is to stop just in time? Neglect
the weight of the driver, and assume that the negative
acceleration of the car caused by the braking is constant
Answers
work = force * distance
30 m in 10 s ... average velocity is ... 3 m/s
final vel is zero , so initial is
... 3 m/s = (vi + vf) / 2 ... vi = 6 m/s
the work is equal to the initial kinetic energy of the car
K.E. = 1/2 m v^2 = 1/2 * (7.50E3 / 9.81) * 6^2 = ? Joules
final vel is zero , so initial is
... 3 m/s = (vi + vf) / 2 ... vi = 6 m/s
the work is equal to the initial kinetic energy of the car
K.E. = 1/2 m v^2 = 1/2 * (7.50E3 / 9.81) * 6^2 = ? Joules