Forces, Motion, and Acceleration Investigation 5, 7, and 9
LT – 1 – I can use data to show what happens when a constant net force is
applied to an object.
1. What would a graph showing balanced forces look like? Draw a position vs. time
Graph and a velocity vs. time graph that show balanced forces.
forces (Constant motion)
When forces are balanced, the motion is constant so the position vs.
time graph can be drawn with a horizontal line (standing still) or with a
straight diagonal line (constant motion). The velocity vs. time graph
can be only a horizontal straight line (constant velocity).
2. What would a graph showing unbalanced forces (net force) look like? Draw a
Position vs. time graph and a velocity vs. time graph that shows unbalanced
forces.
orces.
The position vs. time graph should begin at zero and curve up to the right. (speeding
up). The velocity vs. time graph should be a straight diagonal line going up to the right
(speeding up). Your graphs could also show slowing down and be “unbalanced forces”.
3. Draw a sketch of a position vs. time graph and a velocity vs. time graph that
shows the motion of a wheeled cart when a constant net force is applied.
These two graphs will look just like the graphs you sketched in
number 2.
4. Assume that the graphs you just sketched represent the motion of a wheeled
cart that has one fan providing the constant net force. On the graphs below,
draw three lines: one representing a one-fan cart, one representing a two-fan
cart, and one representing a three-fan cart. (Assume mass is constant).
Your postion vs. time graph should have three curved lines with
the shape in question 2. The least steep line represents 1 fan
and the steepest line represents 3 fans. The velocity vs. time
graph will have three straight diagonal lines. The steepest
represents 3 fans and the least steep line represents only 1 fan.
5. When net force doubles, what happens to acceleration?
It doubles
6. When net force is halved, what happens to acceleration?
It is halved.
7. Draw 2 position vs. time graphs and 1 velocity vs. time graph that would show
unbalanced forces.
Draw graphs that show speeding up and slowing down.
8. Describe in words, the motion of a wheeled cart when a constant net force is
applied.
The wheeled cart will accelerate (speed up)
LT -2 – I can use proportional relationships to make predictions about
force and acceleration.
9. Describe the relationship between net force and acceleration
when mass is held constant.
The relationship is directly proportional. This means
when net force increases so does acceleration. When net
force decreases so does acceleration.
10. A. Calculate the acceleration. B. Graph the line of Fn (net force)
and A (acceleration). C. Name the relationship.
Fn (net
force) N
Mass (kg)
Acceleration
(m/s/s)
10 N
2 kg
5
12 N
2 kg
6
14 N
2 kg
7
16 N
2 kg
8
Net Force and Acceleration
Acceleration (m/s/s)
10
8
6
4
Acceleration
2
0
0
5
10
15
20
Net Force (N)
11. Define directly proportional. What does a directly proportional
relationship look like on a graph? Give an example of this type of
relationship.
Directly proportional means when one value goes up the
other value goes up by a constant ratio. (Double the net
force and the acceleration doubles). When one value
goes down, the other value goes down.
LTLT-3 - I can describe the relationship between mass and acceleration
acceleration of
an object subjected to a constant net force.
12. Describe the relationship between mass and acceleration when the net force
is held constant.
When one value goes up, the other goes down by its reciprocal.
For example, when mass doubles, the acceleration is cut in half.
13. Describe how this relationship looks on a graph.
On a graph, an inversely proportional relationship will form a
curve. The line will begin high on the y axis and will then move
down to the right.
14. A. Calculate the acceleration. B. Graph the line for mass and acceleration.
C. Name the relationship
Net
Force
(N)
10
10
10
10
Mass
(Kg)
Acceleration
(m/s/s)
10
5
2.5
1.25
Mass and Acceleration
Acceleration
10
8
8
6
4
4
Acceleration
2
2
1
0
0
5
10
15
Mass
.
Read each statement. Choose which relationship, A or B fits each statement.
A. Relationship between net force and acceleration
B. Relationship between mass and acceleration
_B___15. When one value is halved the other is doubled.
_A___16. Forms a straight diagonal line when graphed
__A
A__17. When one value decreases the other value decreases by a constant ratio
_B___18. Forms a curved line when graphed
_A___19. Directly proportional
_B___20. Inversely proportional
_B___21. When one value is decreased, the other increases by the reciprocal.
_A___22. When one value increases, the other value increases by a constant ratio.
LT – 4 I can explain how objects exert forces on one another.
Read each statement. Finish the statement with the opposite reaction.
Moon pulls of the Earth
Bug hits car
25. Ball bumps head
26. Spring pulls on man
27. Wall pushes on hand
28. Ball hits bat.
29. A loaded semi-truck and a compact car are on a collision course. Will the semi
exert a greater force on the compact car, or will the compact car exert a greater force on
the truck, or will they exert an equal force when they collide? Explain.
The forces would be equal. Newton’s 3rd Law says for every action there is an
equal and opposite reaction.
30. The earth and moon are attracted to each other by gravitational force. Does
the moon exert a larger force on the moon, or does the moon exert a larger force
on the earth, or are the forces equal? Explain.
The forces would be equal. Newton’s 3rd Law says for every action there is an
equal and opposite reaction.