Question

A 4-kg sled sliding freely on an icy surface experiences a 2 _ N frictional force exerted by the ice and an air-resistive force of 0.5 N.
a. What is the net force acting on the sled?
b. What is the acceleration of the sled?

Answer 1

a.
Both friction and air resistance oppose motion. So the net force is -2N (friction) + -0.5N (air resistance) = -2.5N, where positive is the direction of motion.

b.
F = ma, so a = F/m. You know force and mass, a=?

Answer 2

a. -2.5
b. 0.625