PHYS 1P21 Lecture Notes - Lecture 28: Net Force, Kinematics, Extreme Skiing

• School: Brock University
• Department: Physics
• Course: PHYS 1P21
• Professor: Santo D' Agostino

Document Summary

Example: a person pushes a 12. 3-kg shopping cart at a constant velocity for a distance of 22. 1 m on a flat horizontal surface. She pushes in a direction 23. 6 below the horizontal. Determine the work done by (b)the pushing force, (c)the frictional force, and (d)the gravitational force. Solution: because the velocity of the cart is constant, the net force acting on it is zero. Write newton"s second law of motion for the x-direction and the y-direction: There are two equations and two unknowns (fand n), so we can solve the problem with no further physical analysis. To solve part (a), just solve equation (1) for f: Notice that the sum of the work done by the applied force and the work done by friction is exactly zero. Does this make sense? (after all, the sum of the applied force and friction is zero. )