Physics II Day 4
Net Force
WHAT:
Net force is the total
amount of force placed on an object.
Net force is measured in newtons.
Net force happens in a certain direction.
HOW:
1)
Visualize.
2)
Identify if the forces are
pushing/pulling in the same or opposite direction.
(The question will either use a picture or words)
3)
If the forces are in the same direction, you ADD them.
4)
If the forces are in opposite directions, you
SUBTRACT the smaller
force from the greater one.
It’s like…
Let’s Try as a Class:
1) Letta and Shariah are trying to move a
bookcase towards the corner of a room. Letta pushes on the bookcase with 51
newtons of force. Shariah pushes in the same direction, but she is tired so she
only pushes with 33 newtons of force. What net
force are they exerting on the bookself?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
2) When a rocket takes off, it pushes up
while gravity pulls down. A certain rocket pushes up with a force of 1,220
newtons while gravity pulls down with a force of 840 newtons. What is the net
force upward?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
With Your Shoulder Buddy (at a “one”)
1) Alfredo is trying to move a piano across
his yard into his house. He ties a rope around the piano and tries to pull it
with 34 newtons of force. This doesn’t work, so he gets his sister to help him.
His sister pulls in the same direction with 21 newtons of force. What is the net force they are exerting on the
piano?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
2) Eric is trying to get his brother out of
his room. He pushes on his brother with 32.2 newtons of force. His brother
pushes him back with 16.8 newtons of force. What is the net force exerted out of the room?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
On Your Own (At a “zero”, if you need help you may ask your
shoulder buddy at a “one”)
1) In an arm-wrestling match, Karissa pushes
towards Alex with a force of 60 newtons. Alex pushes in the other direction
with a force of 56 newtons. What is the net
force exerted?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
2) Cristian and his mother are both pushing a
shopping cart. Cristian pushes with a force of 63 newtons and his mother pushes
with a force of 51 newtons. What is the net
force exerted on the cart now?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
3) Use the net force from #2 to find new net force: John Cena walks by and
decides to push against them. They continue to push with the same force, but John
Cena pushes in the other direction with a force of 114 newtons. What is the net force exerted on the cart?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
4) Henri and Jacob are both trying to pull a
boulder off the ground. Henri pulls with a force of 88.21 newtons and Jacob
pulls with a force of 50.1 newtons. What is the net force exerted on the boulder?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
5) Saul’s dog tugs on his leash with a force
of 18.1 newtons while Saul pulls back with a force of 26.3 newtons. What is the
net force exerted backwards?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
6)
Grecia pushes on the crate in the
middle of the table with her finger, exerting a force of 10 newtons. Jesse
pushes in the opposite direction, also with a force of 10 newtons. What is the
net force exerted on the crate?
Circle one: Opposite direction Same direction
 |
Sketch: Solve:
Check Yo Self:
Lifework
Calculate the net force in each scenario. SHOW
YOUR WORK and DRAW THE PICTURE!
1) Someone pushes a bookcase with a force of
30 newtons, and someone else pushes in the same
direction with a force of 18 newtons.
Sketch: Show
Your Work:
Net force: ____________ N
2) Luis tries to pull a boulder up with a
force of 60 newtons. Jose also tries
to pull the boulder up with a force of 67 newtons.
Sketch: Show
Your Work:
Net force: ____________ N
3) Payton tries to pick up a boulder with a
force of 81 newtons, Jose tries to push it down with a force of 77 newtons.
Sketch: Show
Your Work:
Net force: ____________ N
4) A rocket has an upward thrust of 1,567
newtons. Gravity pushes down with a force of 1,200 newtons.
Sketch: Show
Your Work:
Net force: ____________ N
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