Newton’s Three Laws: Sort, Solve and Explain

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Science · Physics
SP-PHYS-003 · Free to print and use in your classroom · substituteplans.com
Page 2
Newton’s Three Laws: Sort, Solve and Explain
Science · Physics · Grades 9-10 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write F = m × a and weight = m × g on the
board, with g = 9.8 m/s².
Technology
None. A calculator is helpful but not required.
Student
independence
High. Students work alone, then share answers with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Whiteboard or chalkboard, Calculators (optional)
Goal for today: Students will identify which of Newton’s laws explains a situation and will use F = m × a to find force,
mass or acceleration.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: Law 1 (inertia): no net force means no change in motion. Law 2: F = m × a. Law 3: every
action force has an equal and opposite reaction force.
☐ Also write: weight = m × g, where g = 9.8 m/s². Force is measured in newtons (N).
☐ Keep the answer key on your desk. You do not need to solve anything yourself.
Say this to start
Good morning! Today’s physics work is about Newton’s three laws of motion. First you will decide which law explains
some everyday situations, then you will solve a few short force problems. The three laws are on the board. Work on
your own at first and then compare answers with a neighbor.
Run of show
Minutes
What you do
What students do
0–5
Take attendance. Hand out the worksheet.
Settle in and take out a pencil.
5–12
Read the three laws on the board aloud. Add this example:
a hockey puck sliding on smooth ice keeps going unless
something pushes on it (Law 1).
Listen and copy the laws if they like.
12–20
Tell students to complete Part A, the table (six situations).
They write 1, 2 or 3 for the law that best fits.
Choose a law for each situation.
20–36
Tell students to complete Part B (problems 1–5). Remind
them to write the formula first. Walk the room.
Substitute the numbers and solve with
units.
36–44
Tell students to do Part C (questions 6–11). Then read the
answers from the key aloud, including the Part A table.
Finish, then mark their work.
44–50
Collect the worksheets in one stack.
Hand in the worksheet.

SubstitutePlans.com
Science · Physics
SP-PHYS-003 · Free to print and use in your classroom · substituteplans.com
Page 3
If things go wrong
• If students confuse mass and weight, remind them: mass is in kg, weight is a force in newtons, and weight =
m × 9.8.
• If students argue about a Part A situation, tell them to pick the law that best fits and write a short reason in
the margin. Some answers can reasonably differ.
• If students ask what a net force is, say: “It is the total force after you add forces in the same direction and
subtract forces in opposite directions.”
• If students finish early, use the early finisher list.
Early finishers
• Write one new everyday example for each of Newton’s three laws.
• Find your weight in newtons if your mass is 55 kg (use g = 9.8).
Support and challenge
• Support: Have students do problems 1, 2 and 4 and the table only.
• Challenge: A 1500 kg car has a net force of 4500 N. Find its acceleration, then its speed after 6 s starting from
rest.
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:
Anything the teacher should know: