Effects of Forces

• Define force

  A push or pull that acts on an object due to the interaction with another object
• What forces produce a resultant force?

  Unbalanced forces
• Resultant force

  A single force that represents the combined effect of all forces acting on an object.
• An object is travelling forward at a constant speed in a straight line. A force is applied perpendicular to the direction of the object's motion. What is the effect of the force on the object's motion?

  The object will change direction
• Define constant velocity

  Motion at a steady speed and in a straight line
• How might a force affect an object?

  Changes in speed

  Changes in direction

  Changes in shape
• Define Newton's first law of motion

  Objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
• Marcy did some online research and found out that the Moon orbits the Earth at a constant speed of around 2000 mph. She says that this is not an example of Newton's first law of motion. Is Marcy correct? Explain.

  Marcy is correct

  The Moon moves with a constant speed, but always changes direction

  So it's not moving with a constant velocity, and is not an example of Newton's first law of motion
• Define Newton's second law of motion

  The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the object's mass
• How does Newton's second law build on his first law?

  His first law states that an object in motion will change if acted upon by a resultant force, and his second law describes that change in motion
• What is the equation for Newton's second law?

  Force= mass x acceleration

  F=ma
• Define Hooke's Law

  The extension of a spring is proportional to the applied force
• What is the equation for Hooke's law?

  Force= spring constant x extension

  F= kx
• What does Hooke's law describe?

  The relationship between the extension of a spring and the applied force, stating that they are proportional
• What does the elastic limit represent in Hooke's law?

  The point beyond which an object will no longer return to its original length when stretched, violating Hooke's law.
• Define circular motion

  The movement of an object along a circular path, where the object's velocity is constantly changing due to the change in direction
• In circular motion, an object's speed may be constant. Describe the velocity.

  Constantly changing
• How does a force cause an object to change direction in circular motion?

  When it acts at 90 degrees to the direction of travel
• What factors determine the force needed to maintain circular motion?

  The factors depend on the mass of the object, the speed of the object, and the radius of the circular path
• What two factors are affected by the size of the radius of an object in circular motion?

  How large the circular path is and the force required to maintain the motion
• State an example of circular motion

  A satellite orbiting a planet
• The radius of an object in circular motion will decrease if the force is increased providing that the mass and speed remain constant
• For an object in circular motion, an increased mass requires an increased force to keep the speed and radius constant
• Define friction

  The force between two surfaces that impedes motion and produces heating
• Define fluids

  Substances that can flow and take the shape of their container
• Define drag

  The frictional force acting on objects moving through fluids, caused by collisions with the gas or liquid particles