\a stone is dropped from the top of a cliff. it hits the ground below after 3.80s. how high is the cliff in meters?
1 answer:
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<h2>Right answer: It follows a curved path
</h2>
The movement of a projectile is a movement in two dimensions (forming a curved path: a parabola shape) with <u>constant acceleration. </u>
<u> </u>
A projectile is any body or object that is thrown or projected by means of some force and continues in motion by its own inertia. This means the only force that acts on it while in motion is <u>the acceleration of gravity</u> (in this case we are on Earth, so the gravity value is ).
Where gravity influences the <u>vertical movement</u> of the projectile, while <u>the horizontal movement</u> of the projectile is the result of the tendency of any object to remain in motion at a constant speed (according to Newton's 1st law of motion sometimes called Law of Inertia).
The other options are <u>incorrect</u> because are <u>false</u>:
-The forward motion negates air resistance: There is always at least a small percent of air resistance, as long as that movement is done on Earth.
-It has variable acceleration: In projectile motion acceleration is constant (gravity acceleration) .
-It is unaffected by gravity: The only force that acts on the projectile is due gravity.
Answer:
A. ) K =126. 7 J
B. ) h= 91.1 m.
Explanation:
A)
- Assuming no air resistance, once released by the pitcher, the speed must keep constant through all the trajectory, so the kinetic energy of the ball can be expressed as follows:
B)
- Neglecting air resistance, total mechanical energy must be the same at any point, so, if we choose the ground level as the zero reference level for the gravitational potential energy, and assuming that the ball attains this kinetic energy just before striking ground, this value must be equal to the gravitational potential energy just before be dropped, so we can write the following equality:
⇒ m*g*h = 126. 7 J
- Solving for h, we get: