Kinematics and Dynamics

Question 1

Vectors v. Scalars

Answer 1

• Vectors has magnitude ( number) and direction ( represented by arrow). Scalars are just magnitudes.
  The vector can be bolded.
• Vectors: Displacement, Velocity, acceleration, force.
• Scalars: distance, speed, energy, mass. Represented by italics.

Question 2

Resultant

Answer 2

To find the result of the interaction between two vectors. Tip-to-tail method results in a greater vector and you add them. Vectors opposing ( opposite direction) each other you subtract them.

• The length of the vectors must be proportional to the magnitude.

Question 3

We can also find the resultant by breaking vectors into individual components, how?

Answer 3

We find the resultant vector by finding the hypothenuse.

Question 4

Displacement v. Distance

Answer 4

Displacement is a vector quantity and only considers the final and initial positions not the total distance it took to go from initial to final positions.

Distance is a scalar quantity and is concerned with the the total distance taken from the initial position to the final position.

Question 5

Velocity

Answer 5

A vector quantity that describes the change in displacement over the change in time.

Question 6

Speed

Answer 6

Speed is a scalar and describes the change in distance over time.

Question 7

Instantaneous velocity

Answer 7

Describes the change in displacement over the change in time as time approaches zero.

Question 8

Force

Answer 8

A vector quantity that is described as a push or pull on an object resulting in a change in velocity.
SI unit: Kg . m/ S^2

Question 9

Gravitational force

Answer 9

The attraction force between two objects.

Fg= G(m1m2/d^2), where G is a constant and is 7x10^-11, m is mass of both objects, and d is distance.

Question 10

What is friction and what are the 2 types?

Answer 10

Friction is a force between two objects that causes them to slow down or stop.

• Static friction (Fs) - friction between a stationary object and it’s surface.
  Fs= ( coefficient of static) x ( normal force)
• Kinetic friction ( Fk)- friction between a moving sliding object and it’s surface.
  Fk= ( coefficient of kinetic friction) x (normal force).

Question 11

Mass

Answer 11

Amount of matter in an object. SI unit is the kilogram.

Question 12

Weight

Answer 12

The effect the gravitational force has on an object. SI unit is the newton.

Question 13

What’s the equation that relates mass and gravitational force?

Answer 13

Fg=M x G

• Fg = gravitational force.
• Mass
• Gravitational force - 9.8

Question 14

Center of mass

Answer 14

The point where the weight of the object is concentrated. This is where gravity acts on the object.

For symmetrical objects it’s at the center, for asymmetrical objects it can be anywhere.

Question 15

Acceleration/ Deceleration

Instantaneous acceleration

Answer 15

Acceleration is the change in velocity over time. SI unit is m/s^2.

Deceleration is acceleration in the opposite direction.

Instantaneous acceleration is the exact same except with time approaches zero.

Question 16

What are Newton’s 3 laws?

Answer 16

1st law ( Law of inertia) - An object at rest will stay at rest and an object in motion will stay in motion unless a force acts on it.

2nd law- When vectors add up it causes an object to acceleration and when they cancel out they don’t have an effect on the object. F=ma

3rd law - For every action there is an equal and opposite reaction.

Question 17

Linear motion

Answer 17

When an object’s movement ( velocity and acceleration) is along a straight line.

Question 18

What forces acts on free falling objects?

Answer 18

gravitational force ( value of -9.8).

If air resistance is not negligible than it acts like friction opposing the free fall. It increases as the velocity increases and is called the drag force.

The point where it’s falling at a constant velocity is referred to as terminal velocity. Happens because the drag force equals the weight of the object.

Question 19

Projectile motion

Answer 19

Motion of an object that follows 2 dimensions and so acceleration and velocity are examined independently in the 2 directions.

The only 2 forces we consider in y direction is air resistance and gravity due to acceleration.

Question 20

What are the forces acting on inclined planes?

Answer 20

The weight of the object ( mg) and the normal force.
Fgy = mgcos(theta)
Fgx= mgsin( theta)
** These are the weights of the objects in the y direction and x direction**

Question 21

uniform circular motion

Answer 21

The centripetal force causes an object to move in a circular path.

• velocity vector is tangential to the centripetal force and always points in a straight line. So if the centripetal force stops, the object will move off in a straight line.
  The tangential force ( force that points in the tangent position) is zero because there is no acceleration of the object.

Centripetal force (Fc) = MV^2/R

Question 22

First condition of equilibrium

Answer 22

For an object to remain at rest all of the vectors acting on it must equal to zero.

Question 23

Translational equilibrium

Answer 23

An object can be in translational equilibrium when the object is at rest or travels at the constant velocity in the same direction.

Question 24

Rotational motion

Answer 24

An applied force at some distance away from the fulcrum provides torque so that arm rotates around the fulcrum.
The distance between fulcrum and applied force is the lever arm.

Torque = d ( lever arm) x F ( force)

If there is an angle between the applied force and the lever arm we multiply the above equation by sin theta.

Question 25

Rotational equilibrium

Answer 25

When the vector forces acting on object cancels out causing not acceleration about the fulcrum.

Question 26

Regarding rotational acceleration, forces that act clockwise are positive , negative? Counterclockwise?

Answer 26

Counterclockwise force will be positive..

Clockwise force will negative.

Question 27

What happens to an object in motion when we suddenly remove the force acting on it?

Answer 27

It will move at a constant velocity.

Because acceleration will be zero therefore there will be no change in the velocity.