Answer to Question #221966 in Physics for caleb villarreal

Question

Identify whether the force identified does positive, negative, or zero work in each of the following situations. A hockey player goes onto the ice: 

 

1. Friction acts on a hockey puck sliding across ice. 

 

2.The normal force acts on the hockey puck as it slides across the ice. 

 

3.Gravity acts on a hockey puck as it falls for a face off. 

 

4.A hockey stick acts on the hockey puck as a player makes a shot on goal. 

 

5.The goalie’s glove acts on the hockey puck, stopping it to make a save. 

Answer 1

By definition, the work is given as the following scalar product:

$$A = \mathbf{F}\cdot \mathbf{d}$$

where $\mathbf{F}$ and $\mathbf{d}$ are force and displacement wectors respectively.

1. Negative. Since friction force acts in opposite direction to the displacement.

2. Zero. Since normal force and the displacement are perpendicular, and the scalar product of perpendicular vectors is zero.

3. Positive. Since the gravity force and displacement point in the same direction during fall.

4. Positive. Since the force applied by the hockey stick and displacement of the puck point in the same direction during shot.

5. Negative. Since the force applied by the glove and displacement of the puck point in opposite directions.