Force and Motion

Question 1

Newtonian mechanics

Answer 1

The velocity of an object can change (object can accelerate) when the object is acted on by one or more forces from other objects

Question 2

Force

Answer 2

Vector. magnitude = acceleration that a force would give to a standard kilogram

Question 3

Net force

Answer 3

Vector sum of all forces acting on the body

Question 4

Newton’s First Law

Answer 4

If there is no net force acting on a body the body remains at rest it is initially at rest or moves in a straight line at constant speed if it is in motion

Question 5

Interial reference frame

Answer 5

Reference frame in which Newtonian mechanics holds.

Question 6

Newton’s Second Law

Answer 6

The net force F(net) acting on a body with mass m is related to the body’s acceleration a by : F(net) = ma

Question 7

Gravitational force F(g)

Answer 7

Force that acts on a body when the body is pull by another body F(g)=mg
g->magnitude of a free-fall acceleration

Question 8

Weight W

Answer 8

magnitude of the upward force needed to balance the gravitational force on the body

Question 9

Normal force F(n)

Answer 9

Force acting on a body from a surface against which the body presses. Always perpendicular to the surface

Question 10

Newton’s Third Law

Answer 10

If a force F(bc) acts on body B due to body C, then there is a force F(cb) acting on a body C due to body B:
F(bc) = - F(cb)

Question 11

1 Newton

Answer 11

1N = 1kg * 1m/s^2

Question 12

Frictional force

Answer 12

Force that acts on a body when force F tends to slide a body along surface. It is parallel to the surface and directed so as to oppose the sliding

Question 13

Static frictional force

Answer 13

Frictional force acting on a body when it doesn’t move.
It’s equal in magnitude and opposite in direction with the component of F that is parallel to the surface.
Has a maximum value f(s,max)=us*F(n)
us- coefficient of static friction

Question 14

Kinetic frictional force

Answer 14

Frictional force acting on a body when it moves. When a body start to moves then frictional force rapidly decreases to a value f(k)=uk*F(n)
uk- coefficient of kinetic friction

Question 15

Drag force

Answer 15

Force that body experience when e is relative motion between a body and some fluid (e.g. air). This force that opposes the relative motion and points in the direction in which the fluid flows relative to the body.
D=1/2C“ro”A(v^2),
“ro”- fluid density
C

Question 16

Effective cross-sectional area A

Answer 16

The area of a cross section taken perpendicular to the velocity

Question 17

Centripetal force

Answer 17

A force that accelerates a body by changing the direction of the body’s velocity without changing the body’s speed.
F=(m(v^2))/R

Question 18

Terminal speed

Answer 18

When a object is falling long enough that the magnitudes of the drag force and the gravitational force on the body become equal. Then this body is moving with terminal speed

Question 19

Uniform Circular Motion

Answer 19

Particle is in Uniform circular motion when it moves in a circle or a circular arc of radius R at constant speed v,