Lesson 4: 2D Motion

Question 1

How do we determine direction in 2D and 3D motion

Answer 1

An angle

Question 2

If acceleration is constant, can we use our kinematic equations in a situation where an object moves in two dimensions?

Answer 2

yes but we must consider the equations in both the x and y directions separatly

Question 3

True or False: You can combine your x and y direction when using your kinematic equations for 2D motion problems

Answer 3

False, you must keep x and y separate. Motion that occurs in one direction does not affect the other.

Question 4

What is projectile motion?

Answer 4

Motion that occurs that occurs in two dimensions where the object is under the influence of the force of gravity.

Question 5

An object is launched from the ground at some angle and returns to the ground. Gravity is the only force acting on the object. What will the trajectory look like?

Answer 5

A parabola

Question 6

What is the x direction acceleration of an object following a projectile motion trajectory?

Answer 6

0 m/s^2, motion is uniform

Question 7

What is the y direction acceleration of an object following a projectile motion trajectory?

Answer 7

-9.8 m/s^2

Question 8

What is the y direction velocity of an object following a projectile motion trajectory at the apex of the motion?

Answer 8

0 m/s

Question 9

An object is launched at 5 m/s at an angle of 30 degrees. What is the x component of this initial velocity?

Answer 9

Vox = 5 cos 30 = 4.33 m/s

Question 10

An object is launched at 5 m/s at an angle of 30 degrees. What is the y component of this initial velocity?

Answer 10

Voy = 5 sin 30 = 2.5 m/s

Question 11

If an object is launched at 7 m/s at an angle of 45 degrees, what will the x component of the velocity be at the apex of the motion if the object follows a projectile motion trajectory?

Answer 11

Vox = constant

Vox = 7 cos 45 = 4.95 m/s

Question 12

An object is launched from the ground a velocity of 4 m/s at an angle of 60 degrees. The object follows a projectile motion trajectory and returns to the ground. What will the y component of the final velocity be?

Answer 12

Voy = -Vfy if perfect parabola

Vfy = -4 sin 60 = -3.46 m/s

Question 13

How do you find the velocity of an object relative to another object already in motion?

Answer 13

Vab = Vae - Vbe

a - object a
b - object b
e - relative to earth (stationary frame of reference)

Question 14

An object is launched horizontally at 8 m/s. Gravity is the only force acting on the object after launch. What will the x component of the initial velocity be?

Answer 14

8 m/s, object is launched horizontally (x direction)

Question 15

An object is launched horizontally at 8 m/s. What will the y component of the initial velocity be?

Answer 15

0 m/s