A compact car of mass accelerates along a straight
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A compact car of mass 1.20×103kg accelerates along a straight, horizontal road. At a particular moment the tires push backward on the road, and the road exerts a 4.00×103N forward frictional force on the tires. At that same moment, resistive forces such as air drag are negligible.
(1) Part 1: Identify the pair of interaction forces associated with the 4.00×103N frictional force, clearly specifying the agent and object for each.
(2) Part 2: Describe a complete free-body diagram for the car at that instant.
(3) Part 3: Determine the car’s acceleration at that instant.
(4) Part 4: If the driver chooses to define the system as “car + Earth,” state the net external horizontal force acting on this larger system and explain what that implies about the horizontal motion of the combined system.
(5) Part 5: Discuss why the equal and opposite forces identified in Part 1 do not cancel when predicting the acceleration you calculated in Part 3.