Unit 4 Two-Dimensional Motion

When analyzing the motion of a projectile the most important concept to understand is that the horizontal component of motion is independent of the vertical motion.

• is that the horizontal component of motion is independent of the vertical motion.

• is that the time of flight is dependent on the horizontal and vertical motion.

• is that the horizontal and vertical components of motion are dependent.

• is that the initial conditions of all projectiles are the same.

Which of the following statements is always true for a projectile?

• The initial vertical velocity is 0 m/s.

• The horizontal velocity is constant.

• The time for the projectile to reach the maximum height is equal to the time it takes to travel down to the ground.

• Air resistance works to oppose the motion of the projectile.

The acceleration of a projectile is

• a constant 9.8 m/s².

• a constant 9.8 m/s² in the negative direction.

• constant in the horizontal and vertical direction.

• changes in the horizontal direction but is constant in the vertical direction.

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Fill in the blank: The acceleration due to gravity is _______.

• 9.8 m/s².

• 10 m/s².

• 8.9 m/s².

• 9.5 m/s².

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As a projectile launched at an angle travels toward the top of its trajectory the vertical velocity (a)   until it reaches the top and is (b)   .

• decreases

• zero

• increases

• constant

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Pair each variable with its correct equation given the following scenario: a pumpkin is launched out of an air cannon at an angle above the horizon with a velocity v₀.

• tan⁻¹(v₀y/v₀x)

• Initial Horizontal Velocity

• v₀cosθ

• Initial Vertical Velocity

• v₀sinθ

• Direction (θ)

A pumpkin is launched from the ground at an angle of 40 degrees above the horizon with a total speed of 60 m/s. Ideally (with no air resistance) the pumpkin will land on the ground with a total speed of

• 0 m/s

• 20 m/s

• 34.6 m/s

• 60 m/s

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In order to find the components of a velocity vector you should

• use right triangle trig to solve (sine, cosine, tangent).

• use the Pythagorean Theorem to determine the magnitude of the components.

• draw the x and y components of the original velocity vector.

• All of these can be used to find the components.

Two projectiles are launched at 100 m/s, the angle of launch for the first being 30°, and for the second, 60°. Which of the following statements is true?

• Both projectiles have the same acceleration while in flight.

• The second projectile has the lower speed at maximum altitude.

• Both projectiles have the same range.

• A, B and C are all true.

• Only A and C are true.

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A projectile is launched from flat ground at an angle θ above the horizon. Match the vector with their correct descriptors.

• Direction changes over time.

• Vertical Displacement

• Both the magnitude and direction change over time.

• Horizontal velocity

• Direction remains constant.

• Horizontal Displacement

• Remains constant in both magnitude and direction.

• Vertical velocity