Force = mass * acceleration or F = ma

Newton’s second law explains why a smaller car gets better gas mileage than a larger car. According to the 2^nd law, the car with the least mass will require less force to make it accelerate than the larger car. Remember that acceleration is a change in speed or direction. If an object is moving in a curved path, its direction is constantly changing. It is constantly accelerating. This means that an unbalanced force must always be present when there is a change in speed or DIRECTION. The acceleration is always in the direction of the unbalanced force.

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  If you apply more force to an object, it accelerates at a higher rate.
  

Three forms of the second law:

As we have heard, in the late 1500’s Galileo dropped 2 cannonballs at the same time from the top of the Leaning Tower of Pisa in Italy. Each cannonball had a different mass. Legend tells us that both cannonballs landed at the same time, helping Galileo form his hypothesis about the motion of falling objects.

All objects accelerate at the same weight regardless of their mass. The acceleration of falling objects is due to the force of gravity between the object and the earth. This is known as ACCELERATION DUE TO GRAVITY. Gravity is the attractive force between all objects in the universe is called gravity. Near the surface of the earth the acceleration due to gravity is 9.8 meters per second per second or 9.8 m/s². But this doesn’t make sense! You have seen that objects fall at different rates with your own eyes!! A rock and a leaf certainly don’t fall at the same rate. As a leaf falls air resistance keeps the leaf from falling as a result of friction. Air resistance also opposes the downward motion of a rock, but the shape of the leaf causes greater air resistance. As the object accelerates through a fall, gravity gradually opposes air resistance until gravity finally overcomes air resistance. Once an object reaches this velocity there is no further acceleration, it has said to have reached terminal velocity.

Isaac Newton proved that the force pulling an apple to the ground was the same force pulling the moon to the earth. Newton’s Law of Universal Gravitation says that all objects in the universe attract one another by the force of gravity. The size of the force depends on 2 factors: the masses of the objects and the distance between them.

1. 
   How much force is required to accelerate a 2 kg mass at 3 m/s²?
   

2. 
   Given a force of 100 N and an acceleration of 10 m/s², what is the mass?
   

3. 
   What is the acceleration of a 10 kg mass pushed by a 5 N force?
   

4. 
   Given a force of 88 N and an acceleration of 4 m/s², what is the mass?
   

5. 
   How much force is required to accelerate a 12 kg mass at 5 m/s²?
   

6. 
   What is the acceleration of a 5 kg mass pushed by a 10 N force?
   

Weight is a measure of the force of gravity on an object. Since weight is a force, its unit is Newtons (N). If your weight is 500 N on Earth, would it be the same on the moon? Explain:

Your weight can also change depending where you are on the Earth. The farther you move from the center, the more your weight decreases. Your weight can changes based on how much gravity is able to pull on you. Is there less of you on the moon or on top of a mountain when you weigh less? Explain.

Before Newton, weight and mass were thought to be the same. Even today, many people refer to weight, but mean mass. Weight is a measure of the force of gravity and mass is the amount of matter. So when you say you want to lose weight, what you are really referring to is mass. Are Mass and Weight related? Yes! Newton’s 2^nd law can be restated in terms of weight (they are both measured in Newtons.