Question

An object is held at an unknown height above Earth’s surface, where the acceleration due to gravity of the object is considered to be constant. After the object is released from rest, a student must determine the object’s speed the instant the object makes contact with the ground.
Which of the following equations could the student use to determine the object’s speed by using the fewest measuring tools if the student does not have access to a motion sensor? Select two answers.

A) vₓ =vₓ₀ +aₓ t
B) x= x₀ + vₓ₀ t + (1/2)aₓt²
C) v²x=v² x₀+2aₓ (x−x₀ )
D) v¯=(x−x₀) /t

Answer 1

Answer:

Options A and B.

Explanation:

Gravitational acceleration, initial height, intial speed and time are required to determine final speed. The option D is incorrect, since speed varies in time. Option C is dimentionally wrong.

The correct strategy is calculating the initial height from option B. Later, substituting time in equation A to derive an expression of the final velocity in terms of position. Hence, the required equations are options A and B.