Forces, Energy and Power

Definition of ‘work done’ (unofficial)

The amount of energy transferred when an external force causes an object to move over a certain distance.

Definition of power (unofficial)

The rate at which power is transferred

Newton’s first law (unofficial)

An object will remain at rest or continue to move with constant velocity unless acted on by an unbalanced force.

Newton’s second law (unofficial)

When an object is acted on by unbalanced forces, the magnitude of acceleration is directly proportional to the size of unbalanced force.

F=ma

Newton’s third law (unofficial)

if object A exerts a force on object B, then object B exerts an equal but opposite force on object A

Definition of friction

Friction is a force that opposes the motion of an object. It always acts in the opposite direction to motion.

Definition of tension

Tension is the pulling force transmitted through a rope, string, wire etc. when it is pulled tight.

Definition of momentum

Measure of the motion of a physical object in terms of its mass and velocity

Principle of conservation of momentum

Total momentum before=total momentum

Definition of impulse

Change in momentum

Tension, (sometimes) friction and F_un formula

F_un=T-friction

Horizontal force formula

F_H=Fcos(angle)

Vertical force formula

F_v=Fsin(angle)

Formula for weight down a slope

W_parallel=mgSin(angle)

Formula for weight into a slope

W_{perpendicular}=mgCos(angle

For a particular impact a student uses the equation: Ft = mv – mu to find the value of F.

Which best describes the value that the student calculates?

It is the average force acting on the object during the impact

Which of the following correctly describes an elastic collision?

total momentum and total kinetic energy are conserved

Which formula for parallel force on slope

mgsin$

Which formula for perpendicular force on slope

mgcos$