Work done = Force x Distance
Force = 10 lb = 44.5 N
Work Done = 44.5 N x 15 m
= 667.5 N-m
The final velocity of the rock before it touches the ground is 28 m/s.
Answer:
Explanation:
As the rock is thrown down, this means the acceleration due to gravity will be exerting on the rock. So the rock will be exhibiting a free fall motion. Thus, the acceleration of the rock will be equal to the magnitude of acceleration due to gravity. Then using the third equation of motion, we can determine the final velocity of the rock provided the values for initial velocity, displacement and acceleration is given in the problem itself.
So the acceleration is equal to 9.8 m/s² due to its free fall motion and displacement will be equal to the height of the tower which is given as 30 m. And the initial speed of the rock is stated as 14 m/s. The initial speed is represented as u, final speed is represented as v, displacement is represented as s and acceleration is represented as a.

Then, 2 × 9.8 × 30 = v²-(14)²
v²=784
v= 28 m/s
So the final velocity of the rock before it touches the ground is 28 m/s.
Answer:
The star-sphere discovered by the Greeks and other ancient civilizations which shows the physical location in space of the nearby stars.
Explanation:
The celestial sphere is an ideal sphere, without defined radius, concentric with the terrestrial globe, in which the stars apparently move. Some ancient civilizations such as the Greeks assumed that the stars were attached to a celestial sphere, which revolves around the earth, while our planet is always immobile.
The force exerted by student A with his scooter is 306 N and that of student B is 204 N.
<h3>
Force applied by each student</h3>
The force exerted by each student is calculated from Newton's second law of motion.
F = ma
where;
- m is mass
- a is acceleration
F(A) = 127.5 x 2.4
F(A) = 306 N
F(B) = 120 x 1.7
F(B) = 204 N
Thus, the force exerted by student A with his scooter is 306 N and that of student B is 204 N.
Learn more about force here: brainly.com/question/12970081
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