Varying the amount of force or mass of an object affects the speed, direction, shape, or orientation of an object's motion.
Newton's Second Law of Motion
Any resulting force is equal to mass times acceleration. This is mathematically expressed as (F=ma).
- Force = a push or pull (F).
- Mass = the amount of matter in an object (m).
- Acceleration = rate of change in the velocity (speed) of an object (a).
Forces = Mass x Acceleration
Force = mass x acceleration
If two objects have the same mass and a greater force is applied to one of the objects, the object which receives the greater force will change speeds more quickly. For example if a cart is pushed harder, it will speed up faster. |
If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for a gradual slowing down. For example, the greater the force applied to the brakes of a bicycle, the more quickly it will slow down or stop. |
Changing the amount of force applied to a moving object can also change the direction that the object is moving more or less quickly. For example, a baseball pitched toward the batter may quickly change direction and speed if hit very hard, or may change direction and speed more slowly if hit softly as with a bunt. |
ShapeChanges in the shape of an object depends on the magnitude of the force that is acting on it. For example, two cars that collide traveling at lower speeds will not have as much change in shape as two cars that collide travelling at a faster speed.
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OrientationOrientation is the position of an object.
A force can cause an object's orientation to change. For example, when two cars collide at a faster rate, there will be more change in their orientation. |
Force = Mass x acceleration
If a heavy (more massive) object is in motion, more force must be applied to get the object moving faster. |
If the same force is applied to two objects, the object with the smaller mass will change speeds more quickly. For example if a golf ball and a truck are hit with a golf club with the same force the golf ball will speed up faster. |
In order to slow down or stop a heavier (more massive) object, the force on that object must be greater than for a less massive object. For example, if the same braking force is applied to a small car and a large truck, the car will slow down more quickly. |
It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass. |
ShapeChange in the shape of an object depends on the mass of the object colliding with the object. For example, a heavier car collides with a lighter car. The lighter car will sustain more changes in the shape of the car.
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OrientationA change in orientation can occur when a heavier object collies with a lighter object. For example, if a heavier car collides with a lighter car, the lighter car will have a more noticable change in their orientation.
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Time to experiment with force, mass, and acceleration!
Select Motion
Interactive Guide:
Before you begin check the Force, Values, Masses, and Speed boxes in the top right corner:
Interactive Guide:
Before you begin check the Force, Values, Masses, and Speed boxes in the top right corner:
- What happens to the speed when you increase the force, but keep the mass the same?
- What happens to the speed when you increase the mass, but keep the force the same?
- How can you make the object move the fastest?
- How can you make the object move the slowest?
Video Guide:
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Topic Tips
- Newton's second law states that the greater the mass of an object, the more force it will take to accelerate the object.
- Force = mass x acceleration or F=ma.
- Varying the amount of force or mass of an object affects the speed, direction, shape or orientation of an object's motion.