Topic 2.2: Forces and Dynamics

Question 1

Define weight

Answer 1

the force of gravity on a body

Question 2

What are the components of Free-Body Diagrams?

Answer 2

 its weight acting vertically from the center of mass
 all forces where it is contact with other objects
 any magnetic or electrostatic forces

Question 3

Define friction

Answer 3

o FRICTION: The force which opposes motion when one surface moves over another. It is caused by the roughness of the surfaces.

Question 4

Define normal reaction

Answer 4

o NORMAL REACTION: Two objects in contact each exert a force on the other which is perpendicular to the surface.

Question 5

Define tension

Answer 5

o TENSION: A force produced in a body when opposing forces are stretching it. The opposite is a compression force when two forces are squashing a body.

Question 6

Define upthrust

Answer 6

o UPTHRUST: An upward force on a body which is immersed in a fluid (liquid or gas).

Question 7

Define lift

Answer 7

o LIFT: An upward force on the wing of an aircraft due to the air flowing around it.

Question 8

• 2.2.4: State Newton’s first law of motion

Answer 8

o NEWTON’S FIRST LAW OF MOTION: A body continues to maintain its state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force.

Question 9

Define inertia

Answer 9

o INERTIA: The property of matter which makes it resist acceleration; objects’ resistance to change

Question 10

• 2.2.6: State the condition of translational equilibrium

Answer 10

o TRANSLATIONAL EQUILIBRIUM: When the net force on an object is zero in all directions (ie no linear acceleration).

Question 11

• 2.2.8: State Newton’s second law of motion

Answer 11

o NEWTON’S SECOND LAW OF MOTION: ∑F = ma The rate of change of momentum of an object is proportional to the applied force and takes place in the direction in which the force acts.

Question 12

Define impulse

Answer 12

o IMPULSE: The change in momentum. A vector. Unit is Ns

Question 13

Define linear momentum

Answer 13

o LINEAR MOMENTUM: the product of mass and velocity. It is a vector measured in kgms-1

Question 14

• 2.2.12: State the law of conservation of linear momentum

Answer 14

o LAW OF CONSERVATION OF LINEAR MOMENTUM: The momentum of an isolated system remains constant (ie when no external forces are acting). Or, in any isolated system, the change in momentum is zero.

Question 15

State Newton’s third law of motion

Answer 15

o NEWTON’S THIRD LAW OF MOTION: Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction