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Flashcards in Translational Motion Deck (15):

Scalar vs Vector

  • Scalar: without direction. For example, length, time, mass.  

  • Vector: with direction. For example, displacement, acceleration, force.


Axis-Vector components


Vector-Vector components


Gravity components on slope


Speed vs Velocity

  • Speed: scalar, no direction, rate of change in distance. 

  • Velocity: vector, has direction, rate of change in displacement.


Instantaenous speed vs Instantaneous velocity

SPEED: Instantaneous speed is the speed at an instant (infinitesimal time interval). Instantaneous speed equals instantaneous velocity in magnitude.

VELOCITY: Instantaneous velocity is the velocity at an instant (infinitesimal time interval). Instantaneous velocity has a direction, instantaneous speed does not. The direction of instantaneous velocity is tangent to the path at that point.



Add the following vectors and determine the resultant.:

5.0 m/s, 45 deg and 2.5 m/s, 135 deg

5.0 m/s, 45 deg+ 2.5 m/s, 135 deg= 5.59 m/s, 71.6 deg

MAGNITUDE: 52 + 2.52 = 31.25 whose square root is 5.59

DIRECTION: The x-component of the resultant vector is 5cos(45) + 2.5cos(135) = 1.77 and the y-component of the resultant vector is 5sin(45) + 2.5sin(135) = 5.30. Then, you take the tan^-1(5.30/1.77) which is 71.6 degrees.


Add the following vectors and determine the resultant.

3.0 m/s, 45 deg and 5.0 m/s, 135 deg and 2.0 m/s, 60 deg


x component: 3cos(45) + 5cos(135) + 2cos(60) = -0.414

y component: 3sin(45) + 5sin(45) + 2sin(60) = 7.389

Finding the square root of the sums of the components: 7.401

DIRECTION: tan-1(7.389/-0.414) = -86.79 + 180 = 93.21. 


What are the FOUR equations at constant acceleration?


What happens to the speed at terminal velocity?

At terminal velocity, weight = friction, so the net force is 0. Thus, the acceleration is 0. So, the speed stays constant at terminal velocity.


What will happen to the acceleration with air resistance?

  • The acceleration is no longer constant - it will decrease with time until it gets to zero at terminal velocity. 

  • When there's air resistance, the acceleration will decrease because the force (weight - resistance) is decreasing due to increasing resistance or friction at higher speeds.


What do you use to find the time that a projectile is in air?

Use the vertical component only. 


How do you find how far a projectile traveled?

First get the time in the air by the vertical component. Then use the horizontal component's speed * time of flight


Equation for uniform circular motion


A pool ball leaves a 0.60-meter high table with an initial horizontal velocity of 2.4 m/s. Predict the time required for the pool ball to fall to the ground and the horizontal distance between the table's edge and the ball's landing location.

y = -0.60 m = (0 m/s)•t + 0.5•(-9.8 m/s/s)•t2

t = 0.350 s 

x = (2.4 m/s)•(0.3499 s) + 0.5•(0 m/s/s)•(0.3499 s)2

x = 0.84 m