Unit 4: 2D Motion Review

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 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.

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

• The time for the projectile to reach the maximum height

• The horizontal velocity is constant.

The acceleration of a projectile is

• constant in the horizontal and vertical direction.

• a constant -9.8 m/s.

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

As a projectile launched at an angle travels toward the top of its trajectory the vertical velocity _______​ ​ until it reaches the top and is _________ . Select the two answers

• Decrease

• 0 m/s

• Increase

• Remains the same

• 9.8 m/s

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

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.

A pumpkin launched from an air cannon hits the ground with a vertical velocity of -31 m/s and a horizontal velocity of 33 m/s. What is the total speed of the pumpkin?

• 64 m/s

• 2 m/s

• 45 m/s

• 33 m/s

The time of flight for a projectile

• depends on the horizontal component of the initial velocity.

• depends on the vertical component of the initial velocity

• coming down from its highest point is two times greater than the time it takes to reach the top of its flight.

• increases only when increases the launch angle of a projectile.

Three projectiles are fired at equal speeds but different angles. One is fired at angle of 30 degrees, the second at 60 degrees and the third at 90 degrees. Neglecting air resistance, the projectile to hit the ground first will be the one fired at

• 30 degrees

• 60 degrees

• 90 degrees

• They will all hit the ground at the same time