This page covers the following topics:
1. Newton's first law
2. Objects at rest
3. Objects moving with constant velocity
4. Accelerating objects
Newton's first law states that an object will remain at rest or continue moving at a constant velocity, unless it is acted upon by an external resultant force. When there is no resultant force acting on an object, the object is said to be in equilibrium. Usually resultant force is found by combining forces on the same axis as vectors.
By Newton's first law, an object at rest will have no forces acting on it. An object lying at rest on the ground will only experience its downwards weight and the upwards normal reaction exerted by the ground on it. If an external resultant force is exerted on the object, then the object will no longer be at rest and will accelerate in the direction of the force.
By Newton's First Law, an object travelling at constant velocity must have balanced forces acting on it. If an external resultant force acts on the object, then the object will accelerate in the direction of the force.
By Newton's first law, an object that is accelerating or decelerating must have unbalanced forces acting on it. Newton's second law can then be used to calculate the acceleration using the resultant force acting on the object.
An object is in vertical equilibrium. There are two forces acting on the object horizontally: a 53 N force in the East direction and a 70 N force in the West direction. Describe the object's motion using Newton's first law.
A ball is rolling across the ground at a constant velocity when it is kicked. Explain what happens to the ball in terms of Newton's first law.
State Newton's first law.
A ladder of weight 200 N resting on rough ground is leaning against a smooth wall. The normal reaction exerted by the wall on the ladder is 200 N. Find the normal reaction and the frictional force exerted by the ground on the ladder.
An object is experiencing forces A, B, C and D as shown in the diagram. Explain the relationships which need to hold between these forces for the object to be in equilibrium.
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