A 1290 -kg car is pushing an out-of-gear 2140 -kg truck that has a dead battery.

Question

A 1290 -kg car is pushing an out-of-gear 2140 -kg truck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push horizontally against the ground with a force of 4480 N . The rolling friction of the car can be neglected, but the heavier truck has a rolling friction of 755 N , including the "friction" of turning the truck's drivetrain. What is the magnitude of the force the car applies to the truck?
What is the magnitude FConT of the force that the car exerts on the truck? Use the coordinate system shown in Part B, where upward is the positivey direction and to the right, the direction F ConT points, is the positive x direction.

Explanation / Answer

Mass of Car m1 = 1290 Kg
Mass of Truck m2 = 2140 Kg

Let the Force applied by Car = F Newton
For the car:
4480 - F = m1*a
4480 - F = 1290 * a --------------1

For the truck:
F - Rolling Friction = m2*a
F - 755 = 2140 * a ------------------2

From 1 & 2

4480 - (2140a + 755) = 1290 * a
4480 - 755 = (1290 + 2140) * a  
a = 1.086 m/s^2

4480 - F = 1290 * a
F = 4480 - 1290*1.086
F = 3079 N
Fcont = 3079 N

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