Speeding Up and Slowing Down Activity
As you hopefully noticed in the previous examples, whether
the cart is speeding up or slowing down can not be
determined from only the sign of the acceleration.
There is, thankfully, a pattern that can be used to determine
whether the cart is speeding up or slowing down.
Velocity
Acceleration
Speeding Up or Slowing
Down
#1
(+) or
+ (-)
(+) or
+ (-)
(speedingspeeding
up) or (slowing
up
down)
#2
(+) or
+ (-)
(+) or
- (-)
down down)
(speedingslowing
up) or (slowing
#3
(+) or
- (-)
- (-)
(+) or
up
(speedingspeeding
up) or (slowing
down)
#4
- (-)
(+) or
(+) or
+ (-)
(speedingslowing
up) or (slowing
down down)
When the acceleration is in the same direction as the
motion (velocity) the object is speeding up.
(++ or --)
When the acceleration is in the opposite direction of
the motion (velocity) the object is slowing down.
(+- or -+)
5. Up away from the motion detector and then down the ramp
a. Observe the motion of the cart after an initial push without using the motion
detector. Answer the following questions for the cart while coasting.
c. Record the graphs as displayed by the motion detector and circle the correct
answers to the questions.
position
+
0
t
velocity
+
0
t
acceleration
+
0
t
5. Up away from the motion detector and then down the ramp
a. Observe the motion of the cart after an initial push without using the motion
detector. Answer the following questions for the cart while coasting.
+
c. Record the graphs as displayed by the motion detector.
position
+
0
t
velocity
+
0
t
acceleration
+
0
t
a. Observe the motion of the cart after an initial push without using the motion
detector. Answer the following questions for the cart while coasting.
c. Circle the correct answers to the questions.
Up the hill
i. Is the slope (constant), (increasing) or
(decreasing)?
+
position
ii. Is the slope (positive) or (negative)?
velocity
iii. This slope represents the cart’s
?
Down the hill
0
t
i. Is the slope (constant), (increasing) or
(decreasing)?
ii. Is the slope (positive) or (negative)?
iii. This slope represents the cart’s
velocity
+
velocity
?
Velocity vs. Time
0
t
i. Is the slope (constant), (increasing) or
(decreasing)?
ii. Is the slope (positive) or (negative)?
iii. This slope represents the cart’s
acceleration
?
acceleration
+
0
t
d. Draw a motion map including both velocity and acceleration vectors.

x
e. Is the velocity positive or negative? + then - f. Is the acceleration positive or negative? Does the direction of the velocity change? yes Does the direction of the acceleration change? no