Forces

Question 1

Normal Force?

Answer 1

The perpendicular force exerted by a surface on an object in contact with it.

Question 2

Frictional Force due to a surface?

Answer 2

The force that opposes the motion of an object and acts parallel to the surface with which the object is in contact with.

Question 3

Coefficient of Friction?

Answer 3

Known as _ and is an indication of the relative roughness of a pair of surfaces in contact.

Question 4

Static Friction?

Answer 4

Means that the object is stationary. As the applied force increases, the force of static friction also increases, staying equal and opposite to the applied force until it reaches a maximum value called Fs(max), just before the object starts to move. For a pair of surfaces in contact, Fs can have any value up to the maximum.

Question 5

Kinetic Friction?

Answer 5

The force acting in the opposite direction to motion while the object is currently in motion. Less force is required to keep an object sliding at constant velocity than to start it sliding in the first place. Thus, Fk is smaller than Fs(max). For a pair of surfaces in contact, Fk can only have one value.

Question 6

Tension Force?

Answer 6

The force that acts along a rope supporting or pulling an object. It is considered to be the same in magnitude on both ends of the rope. Just remember, tension is the same per rope; tension in one rope won’t be the same in another.

Question 7

Compression Force?

Answer 7

Is a pushing force that acts along a rigid light rod, towards the object.

Question 8

Force Diagram?

Answer 8

Decent picture of the object with all the forces drawn in arrows and labelled in full. Even the forces in equilibrium.

Question 9

Free Body Diagram?

Answer 9

Object is represented by a dot with all forces drawn as arrows pointing away from the dot. Forces labelled in full.

Question 10

Vector Diagram?

Answer 10

Diagram obtained by adding the vectors from tail to head. The resultant vector is the vector from the beginning of the first vector (tail) to the end of the last vector (head). Most of the vector diagrams you might encounter are triangular in shape.

Question 11

Constant velocity?

Answer 11

Means an object is in equilibrium, has no net force acting which in turn means the sum of all the forces acting on it equals zero. These same points are true for an object that is stationary. Beware, when a question uses the words “minimum force” it’s talking about constant velocity and that Fnet = 0.

Question 12

Inertia?

Answer 12

The property of an object that causes it to resist a change to its state of rest or uniform motion. To elaborate, if an object is stationary → it will try to remain stationary. If an object is in motion → it will try to continue moving at the same speed and direction.

Question 13

Weight?

Answer 13

The gravitational force the Earth exerts on any object on or near its surface. Could also be considered as actual weight when N doesn’t equal Fg.

Question 14

Apparent Weight?

Answer 14

The contact force on an object, usually N. When N ≠ Fg, then apparent weight ≠ actual weight. Elaborate the differences in magnitude (upwards and downwards) out loud.

Question 15

Weightlessness?

Answer 15

Occurs when no contact force acts on the object. Objects in free fall are always weightless. Fnet = Fg, since N = 0.

Question 16

Angle of Repose?

Answer 16

The maximum angle of inclination for which the object will remain at rest. When pushed with an external net force, the object will then accelerate in the direction of the net force.

Question 17

Gravitational Field?

Answer 17

The force acting per unit mass.

Question 18

Acceleration Due to Gravity?

Answer 18

The acceleration caused by the gravitational force acting on an object on or near the Earth’s or another planet’s surface. On Earth, g is larger near the poles because the surface is closer to the core and smaller at the equator.