NEWTONS SECOND LAW APPLIED Objective: know: how to calculate force, mass, and acceleration be able to: explain the motion of objects.

NEWTON’S SECOND LAW APPLIED

Objective:

know: how to calculate force, mass, and acceleration

be able to: explain the motion of objects

Daily Quiz

1. What are the three formulas used to calculate Newton’s Second Law?

2. What are the units of measurement used for these calculations?

3. What is the difference between Newton’s Second and First laws?

Newton’s Second Review

The amount of force required to move or stop an object depends on its mass and acceleration

Force = mass x acceleration F = ma

m = f ÷ a a = f ÷ m

Which will move faster? Rank in order of decreasing acceleration (slowest to fastest):

An object with a mass of 1 kg given a force of 1 NAn object with a mass of2 kg given a force of 1 NAn object with a mass of 2 kg given a force of 2 NAn object with a mass of 4 kg given a force of 1 NAn object with a mass of 1 kg given a force of 4 N

An object with a mass of 4 kg given a force of 1 N (.25 m/s2)

An object with a mass of 2 kg given a force of 1 N(.50 m/s2)

An object with a mass of 2 kg given a force of 2 N(1.0 m/s2)

An object with a mass of 1 kg given a force of 1 N(1.0 m/s2)

An object with a mass of 1 kg given a force of 4 N

Steps to Solve

1. Determine the two variables you know

2. Determine the variable you don’t know

3. Decide which formula to use 4. Plug in numbers and do arithmetic

(multiply or divide) 5. Solve

Examples

2. If a 1-N net force accelerates a 1-kg mass at 1m/s2, what is the acceleration caused by a net force of 2N on a 2-kg mass?

M = 2 kg F = 2N A = ? A = f ÷ m A = 2N ÷ 2 kg A = 1 A = 1m/s2

6. What is the weight on earth of a girl with a mass of 30 kg (acceleration due to gravity on Earth is 9.8 m/s2)?

A= 9.8 m/s2 M = 30 kg F = ? F= m x a F = 9.8 m/s2 X 30 kg F = 294 F = 294 N

CALCULATING FORCE WORKSHEET1. A man hits a golf ball (0.2 kg) which accelerates at a rate of 20 m/s2. What amountof force acted on the ball?2. You give a shopping cart a shove down the isle. The cart is full of groceries andhas a mass of 18 kg. The cart accelerates at a rate of 3 m/s2. How much force didyou exert on the cart?3. The wind pushes a paper cup along the sand at a beach. The cup has a mass of 25grams ( = ? kg) and accelerates at a rate of 5 m/s2. How much force (in Newtons) isthe wind exerting on the cup?4. You push a friend sitting on a swing. She has a mass of 50 kg and accelerates at arate of 4 m/s2. Find the force you exerted.5. How much force would it take to push another, larger friend who has a mass of 70kg to accelerate at the same rate of 4 m/s2?6. A worker drops his hammer off the roof of a house. The hammer has a mass of 9kg, and gravity accelerates it at the usual 9.8 m/s2. How much force does the earthapply to the hammer?7. A car whose mass is 1000 kg is traveling at a constant speed of 10 m/s. Neglectingany friction, how much force will the engine have to supply to keep going the samespeed? (tricky question) (think INERTIA) ( look at the units)Calculate the force in the following problems by using the equation:Force = mass x acceleration F = m x aBe sure to(1) ALWAYS write the equation, (2)plug in the numbers and units,and (3) give the answer with the correct units.

Big Ideas

We will create a chart of the big ideas and important things that we have covered so far The most essential things that someone would

need to know to be successful in this unit This chart will be left up to help you

remember what you have discovered and show how much you now know that you didn’t realize 10 minutes as a group to decide what to put on

your poster 5 minutes to post your thoughts

Introduction to Newton’s Third Law For every action there is an equal

but opposite reaction

Touch This! Clip Newton’s Third Law Science Theatre

Background Knowledge Acquisition Read p. 360 – 366 Answer questions 1 – 5 on page 366 Devise a workable definition of

Newton’s Third Law and an example Put this information into your graphic

organizer from last time (should now be able to complete your entire chart)

Newton’s Third Law

For every action there is an equal but opposite reaction When you push on the wall, the wall pushes

on you with the same amount of force Impact differs but force is the same

Reflection

How do you remember Newton’s Laws How do they relate How are they different Objective score and rationale