Net Force
A box has a 10 N force pushing right and a 10 N force pushing left.
What is the net force?
0 N
What equation is used to calculate net force?
Fnet = ma
Friction is a force that generally acts:
A. In the same direction as motion
B. Opposite the motion
C. Straight upward
D. Straight downward
B. Opposite the motion
If the net force on an object increases while its mass stays the same, what happens to acceleration?
Acceleration increases.
On a ticker tape, dots that are equally spaced represent:
A. Increasing acceleration
B. Decreasing acceleration
C. Constant velocity
D. No motion
C. Constant velocity
If the net force acting on an object is 0 N, the forces are:
A. Unbalanced
B. Balanced
C. Increasing
D. Frictionless
B. Balanced
A 10-kg block accelerates at 4.5 m/s².
Calculate the net force.
F = ma
F = (10)(4.5)
F = 45 N
A student pushes a box with 20 N of force. Friction pushes back with 5 N.
What is the net force?
15 N
If the force acting on an object is doubled and its mass stays the same, what happens to acceleration?
A. It is cut in half
B. It stays the same
C. It doubles
D. It quadruples
C. It doubles
On a ticker tape, the spaces between dots are getting larger.
What does this tell you about the object's motion?
The object is accelerating/speeding up.
block is accelerating to the east.
Are the forces acting on the block balanced or unbalanced?
Unbalanced
A 5-kg object experiences a net force of 20 N.
What is its acceleration?
a = F ÷ m
a = 20 ÷ 5
a = 4 m/s²
A student applies 35 N of force to a 10-kg block. The block accelerates at 3 m/s².
What is the net force?
Fnet = ma
Fnet = (10)(3)
30 N
If the mass of an object doubles while the net force stays the same, what happens to acceleration?
The acceleration is cut in half.
On a ticker tape, the spaces between dots are getting smaller.
What is happening?
The object is slowing down (negative acceleration).
A 20 N force acts to the right and a 5 N force acts to the left.
What is the net force?
15 N to the right
An object has a mass of 10 kg and experiences a net force of 30 N.
What is its acceleration?
3 m/s²
Using the previous question:
The applied force is 35 N and the net force is 30 N.
What is the frictional force?
35 N − 30 N = 5 N
Which object has the greatest acceleration?
Object Net Force Mass
A 10 N 5 kg
B 10 N 2 kg
C 100 N 5 kg
D 100 N 2 kg
D
Which ticker tape would represent an object moving at constant velocity?
A. • • • • •
B. • • • • •
C. • • • • •
D. • • • • • • • •
A or D — the dots are evenly spaced.
A box has a net force of 0 N. Does that automatically mean the box is not moving?
No. It could be moving at a constant velocity.
An object accelerates at 2 m/s² when a net force of 40 N acts on it.
What is the object's mass?
m = F ÷ a
m = 40 ÷ 2
m = 20 kg
A student applies 50 N to an object. The object accelerates at 1.5 m/s², and friction is 2.5 N.
What is the mass?
First find net force:
50 − 2.5 = 47.5 N
Then:
m = F ÷ a
m = 47.5 ÷ 1.5
Answer: about 32 kg
A 15-kg object experiences a net force of 450 N.
What is its acceleration?
Answer:
a = F ÷ m
a = 450 ÷ 15
a = 30 m/s²
A ticker tape shows:
• • • • • •
What does this tell you?
C. The object is accelerating.