Kinematics

Question 1

Kinematics

Answer 1

Study of an object’s motion in terms of its displacement (position in space), velocity (how fast an object is changing postition), and acceleration (how fast an object is changing its velocity)

Question 2

Displacement

Answer 2

Refers to an object’s change in position

• Vector quantity, must incorporate net direction
  
  • Vector which points from object’s intitial position to its final position
• Δs
  
  • Δx, horizontal displacement
  • Δy, vertical displacement
• SI unit for displacement is the meter, m

Question 3

Distance

Answer 3

Distance, d: length of path/trip

• Distance is not the magnitude of the displacement unless the object has moved in a straight line

Question 4

Speed

Answer 4

Average speed: ratio of the total distance traveled to the time required to cover that distance; total distance/ time

• Speed is a scalar quantity

Question 5

Velocity

Answer 5

Vector that embodies both speed and direction

• Symbolized
• Average velocity: displacement/ time; ^-v^- (v bar, v average) = Δs/Δt

Question 6

Speed Vs Velocity

Answer 6

• Speed has no direction and is always taken as positive
• Velocity is speed and direction
• The magnitude of the average velocity is not called the average speed
  
  • Average speed is the total distance traveled divided by the elapsed time
  • Average velocity is the net distance traveled divided by the elapsed time
  • Average speed is not the magnitde of the average velocity unless the object has moved in a straight line

Question 7

Acceleration

Answer 7

Rate of change of an object’s velocity

• average acceleration= change in velocity/time
  
  • ^-a^-= Δv/Δt
  • Because Δv is a vector, ^-a^- is also a vector; and because Δt is a positive scalar, the direction of ^-a^- is the same as the direction of Δv
• If an object’s original direction of motion is positive, then an increase in speed corresponds to a positive acceleration
  
  • Decrease in speed corresponds to a negative acceleration (decceleration)
• An object can accelerate even if its speed doesn’t change; acceleration depends on Δv
  
  • Velocity changes when, speed is changed, direction is changed, or both speed and direction is changed
• If velocity and acceleration are perpendicular, the object is turning with constant speed
  
  • If a= 0 in the direction of v, the object’s speed is not changing though its velocity may be, if there is acceleration perpendicular to the velocity

Question 8

Uniform Acceleration

Answer 8

• Motion in which the acceleration is constant
• If acceleration is constant ^-a^-= a

Δs= 1/2(v₀ + v)t

Δs= v₀t + 1/2at²

Δs= vt - 1/2at²

v= v₀ + at

v²= v₀² + 2aΔs

Question 9

Free Fall

Answer 9

An object experiencing only acceleration due to gravity

• Near the surface of the earth, the gravitational acceleration has a constant magnitude of about 10 (9,8 m/s²)
  
  • The gravitational acceleration vector, g, points downward
  • In kinematic equations, a is constant (g)
• In the absence of air resistance, all objects fall with the same uniform acceleration; two objects of different sizes and weights such as a hammer and feather dropped from the same height will hit the ground at the same time

Question 10

Projectile Motion

Answer 10

An object launched at an angle other than straight upward, with only the effect of acceleration due to gravity considered, will travel along a parabolic trajectory

• Force of gravity causes an object to fall but does not affect the object’s horizontal motion
• v_0x, the horizonal component of the initial velocity, is equal to v₀cosθ₀
• v_0y, the vertical component of the intial velocity, is equal to v₀sinθ₀
  
  • _​θ₀ is the launch angle
• Once a projectile is launched, its horizontal velocity remains constant during the entire flight
• The full horizontal displacement of a projectile is called the projectile’s range