H Physics

Per 4 Work and Energy

Introduction:

Theoretical:

When work is done on an object, energy is transferred to that object To put in simple terms, energy is the measurement of the work an object can do. What work is is the transfer of one’s physical energy to another by using the applied force that moves in the direction of the force, where the force travels. The traveling direction of the force is called distance as it includes where the object is going. The equation for work is

W = F ∙ D

(Work equals force applied multiplied by the distance traveled). The lab will also explore kinetic energy ( K = 12 mv2 ). Kinetic energy is an expression where a moving object can do work on anything the object hits and quantifies the amount of work the object could do as a result of the motion. Another concept explored is called gravitational potential energy ( U g = mgh mass ∙ gravitational force ∙ height ). Gravitational potential energy is energy an object possesses because of its position in a gravitational field. The most common use of gravitational potential energy is for an object near the surface of the Earth where the gravitational acceleration can be assumed to be constant at about 9.8m/s2 . These three concepts relate to each other as it describes the exchange of energy between interacting systems, commonly known as thermodynamics. Practical:

In the lab report, the two main purposes of the lab are to demonstrate the relationship between work and energy and to determine the variables that affect kinetic energy. The principles the experiment is under is that gravitational potential energy. Mechanical energy is conserved and all of the initial U g gets changed to kinetic energy. Experimental

As there are two sets of experiments, one to measure how mass affects kinetic energy and one for how velocity affects kinetic energy, the rules for both of them will be slightly different. Overall, Supplies needed for the mass experiment includes a cart, a ramp, 5kg weights, half a manila folder, a stopwatch, and meter sticks.

For mass:

1. Set up a ramp on the floor for the cart to roll off, setting the height to .3 meters.

2. The cart by itself is .5kg

3. Set up the barrier 2 meters and the length of the cart away from the bottom end of the ramp for the cart to hit. (Keep in mind that when doing the experiment, multiple tries may be needed as the cart may stray over. Getting a straight hit is essential.) 4. To keep the factors constant as much as possible, place the cart at the very top of the ramp.

5. There will be a timer who will time from the moment the entire cart is off the ramp to the moment the front of the cart starts to hit the barrier. Keep in mind that velocity is 2 meters per second.

6. Record the distance of the barrier travels before being stopped by friction for the calculations and find out how much kinetic energy the cart had

7. Do these steps for four different masses, increasing by each 5kg weights added to the cart. *note that the following charts have insufficient data as the data lacks one more trial for mass and velocity.

For velocity:

1. Velocity is practically the same steps as mass with the exception of the mass as the mass stays the same.

2. To change the velocity of the cart, the ramp height can be changed. Because the bottom end of the ramp shifts, the measured 2 meters will shift positions along with the bottom end.

3. Aside from the first ramp height, do the same for three other heights.

Data Trial 1 m1 = 5kg h=.1 m

time(s)

velocity

(m/s)=2/t

distance (m)

U g = mgh

W = F gD

.5

3.37s

.593

.37

.49

3.626

.5

3.47s

.576

.6

.49

5.88

.5

3.44s

.581

.71

.49

13.803

Averages

3.426s

.584

.56

.49

5.488

Trial 2 m2 = 1kg h=.1 m

time(s)

velocity

(m/s)

distance (m)

U g = mgh

W = F gD

1

3.31

.604

.92

.98

5.9192

1