contestada

A ball is thrown straight up from the surface of the earth and travels along a parabolic path before it hits the ground.
Which of the following statements is true concerning the ball if air resistance is neglected?

a. The acceleration of the ball points downward as the ball moves upward.
b. The acceleration of the ball is zero when the ball is at its highest point in the arc.
c. The speed of the ball is negative as it rises.
d. The velocity and acceleration of the ball always point in the same direction
e. The instantaneous velocity of the ball is the same throughout the ball’s flight.

Respuesta :

elcharly64

Answer:

a. The acceleration of the ball points downward as the ball moves upward.

Explanation:

Projectile Motion

When an object is launched up the free air forming angle respect to the ground level, it travels along a parabolic path due to two separate effects:

  • The acceleration of gravity acting downwards in the vertical direction which modifies the speed from the initial value to zero and again in the opposite direction. This acceleration is constant and equals [tex]g=9.8 \ m/s^2[/tex]
  • The constant speed (zero acceleration) in the horizontal direction that makes the object hit the ground at a certain distance from the launch point.

Let's analyze the presented options and find the correct one

a. The acceleration of the ball points downward as the ball moves upward.

This is true. But it's also true that the acceleration points downwards as the ball moves downwards

b. The acceleration of the ball is never zero, as we have pointed out above

c. Then the ball is rising, the speed is positive. It will be negative when the ball starts to fall

d. The velocity is a vector and is directed tangent to the path of the ball, the acceleration is always directed downwards.

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