High School Physics : Understanding the Relationship Between Force and Acceleration
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Example Question #11 : Understanding The Relationship Between Force And Acceleration
An object moves forward with a constant velocity. What additional information do we need to know to determine the force acting upon the object?
The velocity of the object
The force is
The time the object is in motion
The distance the object travels
The mass of the object
The force is
Force is given by the product of mass and acceleration. If an object has a constant velocity, then it has no acceleration.
If an object has no acceleration, then it must also have no net force.
No additional information is needed to solve this question.
Example Question #11 : Understanding The Relationship Between Force And Acceleration
A 
Since the object is moving with a constant velocity, it has no acceleration. Acceleration is only produced by a change in the velocity.
If acceleration is zero, no force is produced. This conclusion comes from Newton's second law:
Since the acceleration is zero:
Example Question #12 : Understanding The Relationship Between Force And Acceleration
A constant force acts on an object, causing it to accelerate along a track, when it suddenly breaks in half. What is the ratio of the initial acceleration of the object to the acceleration of one piece after it breaks if the force remains constant after the break?
Newton's second law states that:
We are told that the force on the object remains constant, even after it breaks in half. The mass of the broken piece will be equal to half the mass of the total object.
Using these values, we can set up equations for the initial and final accelerations.
If the force remains constant while the mass is cut in half, the acceleration of the object will double. The ratio of the new acceleration to the old acceleration will be 2:1. If the question asked for the ratio of the old acceleration to the new one, it would be 1:2.
Example Question #11 : Understanding The Relationship Between Force And Acceleration
What force is required produce an acceleration of 
Newton's second law states that:
We are given the mass of the object and the acceleration. Using these values, we can solve for the necessary force.
Example Question #13 : Forces
A car moves with a constant velocity of 
We need to know the mass of the car in order to solve
We need to know the frictional forces in order to solve
If an object is moving with constant velocity, then its acceleration must be zero.
We can then look at Newton's second law. If the acceleration is zero, then the net force must also be zero.
This means that the gravitational force and normal force cancel out, and the propulsion force of the car cancels out the force of friction. Forces may still be acting in respective directions, but the net sum of these forces is zero.
Example Question #11 : Understanding The Relationship Between Force And Acceleration
Two dogs pull on a 
We need to know the masses of the dogs in order to solve
First we need to find the net force, which will be equal to the sum of the forces on the bone.
Since the forces are going in opposite directions, we know that one force will be negative (since force is a vector). Conventionally, right is assigned a positive directional value. The force to the left will be negative.
From here we can use Newton's second law to expand the force and solve for the acceleration, using the mass of the bone.
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