Newton’s Second Law of Motion

Newton’s Second Law of Motion

• An unbalanced force acting on an object causes the object to accelerate in the direction of the force.

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• You might unconsciously know the Second Law. Heavier objects require more force to move the same distance as lighter objects.

Wagon movesthis way

Force Applied

Unbalanced

Force, Acceleration, and Mass

• The greater the force applied to a given object, the greater its acceleration.

Force, Acceleration, and Mass

• For a given force, the greater the mass of an object, the smaller its acceleration and vice-versa.

Newton’s Second Law in Real Life

• Using Newton’s second law of motion, explain why larger trucks usually need more distance to stop than do smaller trucks.

Formula for Newton’s Second Law of Motion

• FORCE = MASS x ACCELERTATION

• F =force, m= mass, and a =acceleration.

What does F = ma say?

F = ma basically means that the force of an object comes from its mass and its

acceleration.

Something very small (low mass) that’s changing speed very quickly

(high acceleration), like a bullet, can still have a great force. Something

very small changing speed very slowly will have a very weak force.

Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.

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Newton’s second Law con’t.

F= M x A

Force = Mass x Acceleration

the units:-force is measured in Newtons (N)

-1 N= 1kg*1 m/s2

-mass is measured in kilograms (kg)

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• This is an example of how Newton's Second Law works:

Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.5 m/s2. Using Newton's Second Law, you can calculate how much force Mike is applying to the car.

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• F = M x A

• F= 1000 kg x .5 m/s2

• F= 500 k x m/s2

•So F= 500 Nhttp://www.classzone.com/books/ml_science_comp/page_build.cfm?id=none&mod=13

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Examples

• What force is needed to push a 10kg shopping cart at 3 m/s2 ?

• F=m*a

• F= 10 kg*3 m/s2

• F= 30 N

Question

• Identical twins are riding in identical wagons. A friend gives the first wagon a stronger push than the second. Which twin will experience greater acceleration?

Question

• Would a car towing a boat take less, the same, or more time to accelerate than it would without the boat? Explain.

Question

• What will happen to the acceleration of an object if the mass decreases and the force is constant?

Question

• If two identical objects accelerate at the same rate, what must be true of the force applied to each object?