# PHYS 2211 Module 2 Class Activities

## Module 2 Class Activities

These three energetic Huskies are being taken for a walk, but sometimes it’s more like they are taking their walker for a walk. All of a sudden, a car backfires and the bang frightens the dogs, causing them to dart in three different directions.

The gray husky heads due East, pulling with 34 N of force on the leash. The black and white husky turns 56° North of East and pulls with 45 N on the leash. The white husky turns 40° South of East and pulls on the leash with 30 N of force.

To keep the dogs from running away, how hard does the walker need to pull on the leash and in what direction?

An air-conditioning unit is fastened to a roof that slopes at an angle of 35° above the horizontal. Its weight is a force F on the air conditioner that is directed vertically downward. In order that the unit not crush the roof tiles, the component of the unit’s weight perpendicular to the roof cannot exceed 425 N. (One newton, or 1 N, is the SI unit of force. It is equal to 0.2248 lb.)

(a)  What is the maximum allowed weight of the unit?

(b)  If the fasteners fail, the unit slides 1.50 m along the roof before it comes to a halt against a ledge. How much work does the weight force do on the unit during its slide if the unit has the weight calculated in part (a)? The work done by a force F on an object that undergoes a displacement s is W = Fs.