NLM - Newton's First Law

Newton's First Law

Newton's First law of motion states that an object in motion will remain in motion and an object at rest will remain at rest, unless acted upon by an outside force. Forces then, are quantities that cause acceleration, or a change in motion. Forces are defined as pushes or pulls on an object. It is important to remember that objects do not feel what is causing a force, only that the force is causing acceleration. The First Law says that if there is no acceleration, then all the forces acting on it add up to zero. The zero in this case is the vector sum of all the forces acting on the object. Please watch the following presentation that will introduce Newton's First Law of Motion.

Newton's First Law Practice

We will now practice solving problems using the concepts you learned in the presentation. In all the examples, the sum of the forces is equal to zero. Be sure to stay in the habit of showing all work as you solve physics problems. The presentation will give you time to work through the problems, find a solution, and check your work.

Newton's First Law Self-Assessment

Now it is your turn. Complete the self-assessment questions to verify that you can calculate the values of forces when the object is at rest or moving at a constant velocity.

  1. A box with a weight of 200N is hanging from two ropes. Both ropes make an angle of 40o to the horizontal. What is the force of each of the ropes on the box? 

R1 points up and right, R2 points up and left, 200N is pointing down

SOLUTION Links to an external site.

  1. Three forces acting on a stationary object are indicated in the diagram below. What is the magnitude of the forces A and B? 

Force A points at 252 degrees, Force B at 160 degrees, and a force pulls 25N at 25 degrees

SOLUTION Links to an external site.

  1. Three men are trying to hold a horse still with ropes tied around him. The first is pulling with a force of 300N at 0o. The second is pulling with a force of 400N at 118o.   With what magnitude and direction must the third man pull to keep the horse from moving?

SOLUTION Links to an external site.

Newton's First Law Practice Problems

Download Newton's First Law Practice Problems Links to an external site..

Download solutions Links to an external site. to the practice problems. 

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