Unit 2 - Physics Notes
, (1) Notes - Work
Monday, March 25, 2019 9:51 PM
- Work is done by a constant force
- Work (W) - the energy transferred to or from an object by means of a force acting on
the object
- Positive Work - the work done when the displacement and the applied force act in
the same direction
- Negative Work - the work done when the displacement and the applied force act in
opposite directions
- Joule (J) - SI derived unit for measuring forms of work and energy; equal to the work
done when a force of 1 N displaces an object 1 m in the direction of the force
- W = F(d)
- W = (F)(d)(cos theta) where theta is the angle between the directions of the force
and the displacement
- Work = area under a force vs change in distance graph
- Zero displacement = zero work
- 1 J = 1 Nm
- Example: How much work is done by you pulling a wagon with a horizontal force of
50 N for a distance of 6.4m?
○ Therefore, the work is 320 J.
- Example: A student is pulling a wagon at a constant velocity with a force of 60 N. The
handle of the wagon is at 33 degrees above the horizontal. How much work is done
by the student if she must move the wagon 0.25 km?
○ Therefore, there is 1.3 x 10^4 J of work being done.
- Example: You toboggan to a stop 20.1 m along the horizontal at the bottom of the
hill. The total mass of you and the toboggan is 73.2 kg, and the coefficient of kinetic
friction between the toboggan and the snow is 0.106.
○ Draw a free body diagram of the situation and determine the magnitude of
kinetic friction.
, (1) Notes - Work
Monday, March 25, 2019 9:51 PM
- Work is done by a constant force
- Work (W) - the energy transferred to or from an object by means of a force acting on
the object
- Positive Work - the work done when the displacement and the applied force act in
the same direction
- Negative Work - the work done when the displacement and the applied force act in
opposite directions
- Joule (J) - SI derived unit for measuring forms of work and energy; equal to the work
done when a force of 1 N displaces an object 1 m in the direction of the force
- W = F(d)
- W = (F)(d)(cos theta) where theta is the angle between the directions of the force
and the displacement
- Work = area under a force vs change in distance graph
- Zero displacement = zero work
- 1 J = 1 Nm
- Example: How much work is done by you pulling a wagon with a horizontal force of
50 N for a distance of 6.4m?
○ Therefore, the work is 320 J.
- Example: A student is pulling a wagon at a constant velocity with a force of 60 N. The
handle of the wagon is at 33 degrees above the horizontal. How much work is done
by the student if she must move the wagon 0.25 km?
○ Therefore, there is 1.3 x 10^4 J of work being done.
- Example: You toboggan to a stop 20.1 m along the horizontal at the bottom of the
hill. The total mass of you and the toboggan is 73.2 kg, and the coefficient of kinetic
friction between the toboggan and the snow is 0.106.
○ Draw a free body diagram of the situation and determine the magnitude of
kinetic friction.
