Work and Force and Position
Work - KE Theorem
Potential Energy
Conservation of Energy
Potpourri
100
The net vertical force on a box F as a function of the vertical position y is shown. What work is done by this force as the box moves from y = 0 - 5?
20 J
100
15 m/s
100
What is the significance of the slope on the Potential Energy vs. Position graph?
It is the negative conservative force:
dU/dx = -Fx
100
6.6 m/s
100
C, A, D, B
200
Given that F(x) = 4x, find the work done by this force as an object moves from a position x = 0 to 4 meters.
32 J
200
A truck pushes a pile of dirt horizontally on a frictionless road with a net force of 20 N, for 15 m. (Don't think to hard about the frictionless road).
What kinetic energy does the dirt gain?
300 J
200
0.89 J
200
1m
200
-4.9 J
300
They both hit with the same speed.
300
The graph shows a horizontal force that acts on an object as it varies with position. If the object is initially at rest, and it develops a speed of 4 m/s after moving from 0 to 4 meters. What is the object's mass?
15 kg
300
300
x=0.83m
300
A 2000kg car is moving along at a speed of 20 m/s when the brakes are applied and a 2000N force slows the car to a stop.
What is the power output of the brakes?
-40000 Watts
400
A force is given by the vector F = (4i + 3j)N and acts on an object through a displacement of r = (6j)m. What is the work done on the object?
What if the displacement had been r = (-2i + 3j)m?
18 J
1 J
400
400
Given the potential energy of a system varies with position according to the following equation:
U(x) = 5x4 - 3x + 5
What is the conservative force acting on an object that at a position of 2 m?
-37 N
400
2 m/s
400
A 2000kg car is moving along at a speed of 20 m/s when the brakes are applied and a 2000N force slows the car to a stop.
If the car stops in 50m, how much work was done by the brakes?
-100,000 J
500
-50.5 J
500
100 meters
500
Given the potential energy of a system varies with position according to the following equation:
U(x) = 5x3 - 3x + 5
Find the equilibrium positions
+/- 0.44m
500
x = 1.2m
500
A 2000kg car is moving along at a speed of 20 m/s when the brakes are applied and a 2000N force slows the car to a stop.
Find the speed of the car after 20 m?
19 m/s