A student throws a stone upward at an angle of 45° above the horizontal. Which statement best describes the stone at the highest point that it reaches? (1) Its acceleration is zero. 2) Its acceleration is a minimum, but not zero. 3) Its gravitational potential energy is a minimum. 4) Its kinetic energy is a minimum.
Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
![25 A baseball player throws a ball horizontally.
Which statement best describes the ball's motion
after it is thrown? [Neglect friction.]
(1) Its vertical speed remains the same and its
horizontal speed increases.
(2) Its vertical speed remains the same and its
horizontal speed remains the same.
(3) Its vertical speed increases and its horizontal
speed increases.
(4) Its vertical speed increases and its horizontal
speed remains the same.
26 A red ball and a green ball are simultaneously
thrown horizontally from the same height. The
red ball has an initial speed of 40. meters per
second and the green ball has an initial speed of
20. meters per second. Compared to the time it
takes the red ball to reach the ground, the time it
takes the green ball to reach the ground is
(3) half as much
(4) four times as much
(1) the same
(2) twice as much
27 A student throws a stone upward
45° above the horizontal. Which statement best
describes the stone at the highest point that it
an angle of
reaches?
(1) Its acceleration is zero.
(2) Its acceleration is a minimum, but not zero.
(3) Its gravitational potential energy is a
minimum.
(4) Its kinetic energy is a minimum.
28 A projectile is launched with an initial velocity of
200 meters per second at an angle of 30° above the
horizontal. What is the magnitude of the vertical
component of the projectile's initial velocity?
200 m/s
(1) 200 m/s x cos 30° (3)
cos 30°
200 m/s
(4)
sin 30°
(2) 200 m/s x sin 30°
29 An amusement park ride moves a rider at a
constant speed of 14 meters per second in a
horizontal circular path of radius 10. meters.
What is the magnitude of the rider's centripetal
acceleration in terms of g, the acceleration due to
gravity?
8.
(1) 1g
(2) 2g
30 As a cart travels around a horizontal circular
(3) 3g
(4) 0g
track, the cart must undergo a change in
(1) velocity
(2) inertia
(3) speed
(4) weight](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F83ae677f-f312-496f-8610-92f8e2276b7a%2Fb8639682-93a1-44ac-8bf3-cf69f06d90a8%2Fjy6oz3_processed.jpeg&w=3840&q=75)
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