PHYS 2101

1
PHYS 2101
Spring 2009

• Work Done by Conservative Forces
• Potential Energy
• Conservation of Energy

2
PHYS 2101
Spring 2009
CT1
You need to load a heavy box from the ground onto
the back of a pickup truck. You can (A) lift it
straight up, (B) slide it up a steep, short
ramp, or (C) slide it up a long ramp. What is
the correct order for the work done by gravity in
each case? 1. WAgtWBgtWC 2. WAltWBltWC 3.
WAgtWBWC 4. WAWBWC
You need to load a heavy box from the ground onto
the back of a pickup truck. You can (A) lift it
straight up, (B) slide it up a steep, short
ramp, or (C) slide it up a long ramp. What is
the correct order for the work done by you in
each case? 1. WAgtWBgtWC 2. WAltWBltWC 3.
WAgtWBWC 4. WAWBWC
A
C
B
3
PHYS 2101
Spring 2009
Instead of lifting the box, you need to get it
from the back of the truck to the ground. You
can either (A) drop it straight down, (B) let
it slide down a steep, short ramp, or (C) let it
slide down a long ramp. Rank the situations
according to the speed of the block when it hits
the ground in each case. 1. vAgtvBgtvC 2.
vAltvBltvC 3. vAgtvBvC 4. vAvBvC
Instead of lifting the box, you need to get it
from the back of the truck to the ground. You
can either (A) drop it straight down, (B) let
it slide down a steep, short ramp, or (C) let it
slide down a long ramp. Rank the situations
according to the work done by gravity in each
case. 1. WAgtWBgtWC 2. WAltWBltWC 3. WAgtWBWC 4.
WAWBWC
CT2
A
C
B
4
PHYS 2101
Spring 2009
EX1
What is the gravitational potential energy of a
10 kg box that is 2 m above the ground?
What is the gravitational potential energy of a
10 kg box that is 2 m above the ground if the Ug
0 at the ground?
What is the gravitational potential energy of a
10 kg box that is 2 m above the ground if the Ug
0 at the height of the box?
What is the gravitational potential energy of a
10 kg box that is 2 m above the ground if the Ug
0 at a height of 1 m above the ground?
What is the gravitational potential energy of a
10 kg box that is 2 m above the ground if the Ug
0 at a height of 1 m above the height of the
box?