An attacker at the base of a castle wall 3.60 m high throws a rock straight up with speed 7.50 m/s from a height of 1.60 m above the ground. a) what is its speed at the top? If not, what initial speed must it have to reach the top? b) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 7.50 m/s and moving between the same two points. c) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations? d) Explain physically why it does or does not agree.
Displacement, Velocity and Acceleration
In classical mechanics, kinematics deals with the motion of a particle. It deals only with the position, velocity, acceleration, and displacement of a particle. It has no concern about the source of motion.
Linear Displacement
The term "displacement" refers to when something shifts away from its original "location," and "linear" refers to a straight line. As a result, “Linear Displacement” can be described as the movement of an object in a straight line along a single axis, for example, from side to side or up and down. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Linear displacement is usually measured in millimeters or inches and may be positive or negative.
An attacker at the base of a castle wall 3.60 m high throws a rock straight up with speed 7.50 m/s from a height of 1.60 m above the ground.
a)
what is its speed at the top? If not, what initial speed must it have to reach the top?
b) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 7.50 m/s and moving between the same two points.
c) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations?
d) Explain physically why it does or does not agree.
Given Data:
- The initial velocity is, u = 7.5 m/s.
- The initial height is, y = 1.60 m.
- The final height is, y' = 3.60 m.
(a)
The speed at the top can be calculated as,
Here v is the final speed and g is the acceleration due to gravity whose value is 9.8 m/s2. Substituting the values, we have,
Thus, the speed at the top is 4.13 m/s.
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