Science Lab Report
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manuallabreport2.docSuffolk University
College of Arts and Sciences
Physics Department
SCI-L101-HYB Physical Science Lab I
Lab 02. Motion
Based on virtual apparatus designed in Kentucky Educational Television
(http://virtuallabs.ket.org/physics/)
Instructors
Oleg Kreydin
Igor Kreydin
Introduction
Velocity is vector. It has both magnitude and direction. The magnitude of the velocity is speed.
Acceleration is the rate at which the velocity of a body changes with time. The SI unit of acceleration is the meter per second squared (m/s2).
Acceleration is vector. It has both magnitude and direction. Acceleration may result from a change in speed. While the body is in straight line motion its speed can increase or decrease. Acceleration may result from a change in direction. While car for example makes turn, it changes the direction of the velocity.
If object is moving in straight line under influence of constant force the acceleration of the object is constant. Acceleration may be in the same direction as the velocity or the acceleration may be in the opposite direction from the velocity. If the velocity vector has the same direction as the acceleration vector the object speeds up and the velocity increases. If the velocity vector has the opposite direction as acceleration vector the object slows down and the velocity decreases. In this case acceleration sometimes called deceleration.
In this experiment you will examine the motion of a cart in straight line under influence of a constant force when velocity and acceleration vectors are in the same direction. The force will be supplied by the weight of a hanging mass (M1) that will be used to pull the cart (M2). By varying the mass of the hanging weight and the cart (see Figure 1) you can change the speed of the cart and measure the acceleration of the cart
[
]
[
]
100
cm
A
m
A
=
APPARATUS
This is virtual experiment. The original appearance of the lab setup is shown on Figure.2
The cart and track. A cart with frictionless wheels rolls along a 2-m-long track. Card width (l=10cm)
Changing the Cart’s Mass. Brass masses can be added to the cart to adjust its mass and weight. The mass of the cart can be increase by dragging brass masses and releasing them onto the spindle at the center of the cart. The mouse pointer needs to be near the spindle when you release the mass. The Remove All and Remove Masses buttons remove all masses from the cart.
Adding Hanging Masses. To add mass to a hanger, drag a brass mass and release it when it’s over the silver shaft of the hanger. To remove all masses, click Remove Masses. To remove the strings and hangers too, click Remove All.
The Brake. The brake will stop the cart instantly and hold it against any force. You can drag the cart with the brake on. Click the red brake sign to turn on the brake. It turns green. Clicking again turns off the brake and resets it to red.
The Ruler. Clicking ruler icon turns the ruler on and off. You can drag it up and down the screen as needed. It’s very useful in measuring the position of the cart mast.
Photogates. The photogates in this virtual lab represented on the screen as red dots.
In the figure above the cart is shown passing a gate at the 20-cm point. The flag reads eT=2.136 and dT=0.996. The dT=0.996 is time interval during which the gate is blocked.
Mass of the cart. The mass of the cart MC=250g.
Mass of the hunger. The mass of the hunger MH=50g.
Brass Masses. Brass masses are located at the bottom of the screen. In this lab we use three brass masses: B1=200g, B2=100g, and B3=50g.
Sample Setup
Make Setup (S=20cm, x1=50cm, x2=160cm, M1=MH+B3, M2=MC+B1+B2)
Where:
S-starting position of the cart;
x1- position of the Photogate 1;
x2- position of the Photogate 2;
M1- hanging mass;
M2- cart mass;
MH- mass of the hunger;
MC- mass of the cart;
B1, B2, B3- brass masses
1. Click photogate option and select 2 photogates (Figure 3)
2. Click ruler icon and click the brake (Figure 4)
3. Use mouse to move cart to position 20cm. Use mouse to move photogates to positions
50cm and 160cm (Figure 5)
4. Click ruler icon to turns the ruler off. Click on the red spool (a) of string and drag and release it near the ring on the right (or left) end of the cart. The spool will disappear and a short segment of string will appear (b) between the ring and the hand cursor. Move the cursor horizontally until it passes the pulley on the right end of the track. The string will follow. (c) Move down a bit and scissors will appear. (d) Click and the scissors will disappear and the small loop will appear at the end of the string. (e) Now drag the silver hooked mass hanger (above the spool) and release it when its hook is above the loop. It will fall and catch the loop. (f). (Figure 6 and Figure 7)
5. Add masses B1 and B2 to the cart. It can be done by dragging brass masses and releasing them onto the spindle at the center of the cart. The mouse pointer needs to be near the spindle when you release the mass. Add mass B3 to the hunger. It can be done by
draging a brass mass and release it when it’s over the silver shaft of the hanger.
The Remove All and Remove Masses buttons remove all masses from the cart. (Figure 8)
6. Click Take Gate Data control and click Brake control to release the cart. The screen after this experiment should looks like shown in Figure 9.
7. Click Stop Gate Data, Clear Data Gate, and Remove All controls. You are ready for new setup
Data Processing
1. To convert a value from centimeters to meters you can use equation
Where:
A[m]- value in meters;
A[cm]- value in centimeters
2. To convert a value from grams to kilograms you can use equation
[
]
[
]
1000
g
A
kg
A
=
(2)Where:
A[kg]- value in kilograms;
A[g]- value in grams
3. The distance between the Photogate 1 and Photogate 2 (Figure 1) can be found as
1
2
x
x
d
-
=
(3)Where:
x1[m]- position of the Photogate 1 (Figure 1);
x2[m]- position of the Photogate 2 (Figure 1)
4. The instantaneous speed of the cart at the Photogate 1 can be found from experimental data as
1
1
t
l
v
=
(4)Where:
l[m]- cart length (Figure 1);
t1[s]-time interval during which the Photogate 1 is blocked
5. The instantaneous speed of the cart at the Photogate 2 can be found from experimental data as
2
2
t
l
v
=
(5)Where:
t2[s]-time interval during which the Photogate 2 is blocked (s)
6. Because the cart is moving in straight line under influence of constant force the constant acceleration of the cart can be found as
(
)
d
v
v
a
2
2
1
2
2
-
=
(6)Track
Hanging Mass (M1)
d
Photogate 2
Photogate 1
Cart with frictionless wheels (M2)
l
Figure 1
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Figure 9
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