Dynamics- Newton’s Laws T8

Question 1

Balanced forces + Example

Answer 1

Objects that are either stationary or moving at a constant speeds forces acting oppositely are balanced.
For example a skydiver at terminal velocity since air resistance and weight are balanced.

Question 2

Unbalanced forces + example

Answer 2

Objects that are either accelerating or decelerating as their is a force that is larger than its opposite.
For example a car accelerating since the forward thrust from the engine is larger than the friction + air resistance on the car.

Question 3

Force diagram

Answer 3

Object must be drawn as a box. Forces drawn as arrows.

Question 4

Newton’s First Law

Answer 4

An object will remain at rest or at a constant velocity in a straight line unless acted on by an unbalanced force.

Question 5

Newton’s second law

Answer 5

If an overall resultant (or unbalanced) force is applied to an object, the object will accelerate in the direction of the unbalanced force.

Question 6

Newton’s Third law

Answer 6

For every action there is an equal and opposite reaction.

Question 7

Application of Newton’s second law

Answer 7

F (un) = ma
Unbalanced force = mass x acceleration.
Will often be rearranged to find acceleration. Remember it is the unbalanced force, often a trip up point.

Question 8

Newton pairs

Answer 8

Actions and reactions for example pushing a wall will have the reaction of the wall pushing you

Question 9

Finding weight

Answer 9

W =mg
Weight = mass x gravitational field strength.
Weight will change on other planets whereas mass stays the same. Weight is in N.
Gravitational field strength is 9.8 on earth, other planets can be found in data booklet.