Projectile Motion

If a ball thrown straight up into the air takes 4 seconds to reach the top (peak), how long will it take to travel from the peak back to the original position?

• 0s

• 1s

• 3s

• 4s

Answer explanation

The time taken to go up is equal to the time taken to come down due to symmetry in projectile motion. Since it takes 4 seconds to reach the peak, it will also take 4 seconds to return to the original position.

The initial horizontal velocity of a projectile is ____ its final horizontal velocity.

• less than

• equal to

• greater than

Answer explanation

The initial horizontal velocity of a projectile remains constant throughout its flight due to the absence of horizontal forces (ignoring air resistance). Therefore, the initial horizontal velocity is equal to its final horizontal velocity.

What is true about the vertical velocity of a projectile launched horizontally?

• It is initially at its maximum value.

• It increases due to gravity as it falls.

• It remains constant throughout its trajectory.

• It decreases as it falls due to gravity.

Answer explanation

The vertical velocity of a projectile launched horizontally starts at zero and increases due to gravity as it falls. This means the correct choice is that it increases due to gravity as it falls.

If two projectiles are launched at two different heights, 2m and 10m, which one will reach the ground first?

• 2m

• 10m

• they both will hit the ground at the same time

Answer explanation

The projectile launched from 2m will reach the ground first because it has a shorter distance to fall compared to the one launched from 10m. Both projectiles fall freely under gravity, but the lower height results in a quicker impact.

Tags

NGSS.HS-PS2-4

Which hits the ground first if they start at the same height: a dropped ball or a ball launched with a

horizontal velocity?

• the launched ball

• the dropped ball

• they both hit at the same time

Answer explanation

Both balls hit the ground at the same time because the horizontal velocity of the launched ball does not affect its vertical motion. They both fall under the influence of gravity equally.

Tags

NGSS.MS-PS2-2

What is the vertical velocity of an object launched straight up at its highest point?

• zero

• equal to its v_x

• ½ its maximum value

• equal to gravity

Answer explanation

At the highest point of its trajectory, an object launched straight up has no vertical velocity, as it momentarily stops before descending. Therefore, the vertical velocity is zero.

Once a projectile is launched, what is the only force that affects its motion?

• mass

• friction

• inertia

• gravity

Answer explanation

Once a projectile is launched, the only force acting on it is gravity, which pulls it downward. Other factors like mass, friction, and inertia do not directly influence its motion in the absence of air resistance.

Tags

NGSS.HS-PS2-4

Which of the following statements about the horizontal and vertical components of projectile motion is true?

• Changes in the horizontal component occur only when the vertical component changes.

• Both the horizontal and vertical components are always constant.

• The vertical component changes while the horizontal component stays the same.

• The horizontal and vertical components are dependent of each other.

Answer explanation

In projectile motion, the vertical component is affected by gravity, causing it to change, while the horizontal component remains constant due to no horizontal forces acting on it. Thus, the correct statement is that the vertical component changes while the horizontal component stays the same.

Victor Velocity is standing on top of the roof of his house, firing stones with his slingshot over a level field. He is aiming straight outward, horizontally. If Victor pulls back harder on the sling to shoot a stone, which of the following quantities will be changed?

• The vertical displacement of the stone.

• The distance the stone travels, and the horizontal velocity.

• The time it takes the stone to strike the ground, and the horizontal velocity.

Answer explanation

When Victor pulls back harder on the sling, he increases the stone's initial speed, which changes the horizontal velocity and allows the stone to travel further. The vertical displacement and time to strike the ground remain unchanged.

Tags

NGSS.HS-PS2-1

What is the sign of vertical acceleration at point B

• +

• -

• 0

Answer explanation

At point B, the vertical acceleration is negative (-) because the object is likely moving downward or decelerating in the upward direction. This indicates a net force acting downward, resulting in negative acceleration.

Tags

NGSS.HS-PS2-1