A 0.15-kg ball is thrown into the air and rises to a height of 20.0 m. How much kinetic energy did the ball initially have?

Answers

Answer 1
Answer: IF the toss was straight upward, then the kinetic energy it got
from the toss is the gravitational potential energy it has at the top,
where it stops rising and starts falling.

Potential energy =  (mass)  x   (gravity) x (height)

                           = (0.15 kg) x (9.8 m/s²) x (20 m)

                           =      29.4 kg-m²/s²  =  29.4 joules .
Answer 2
Answer: The conservation of energy says that energy in an isolated system remains constant, that it is not created nor destroyed but transforms from one form of energy to another. 
So when the ball is thrown into the air, it has kinetic energy (KE). As it goes into the air, that kinetic energy transforms into gravitational potential energy (GPE). The higher it gets, the more GPE it has and therefore the less KE it has. 
At the top, all of it is transformed into GPE and there is no KE.
But total energy at any point after the ball is thrown until it lands it has the same energy throughout. 

Knowing this, you can set the beginning KE equal to the final GPE. 
KE = GPE

Insert formula for GPE.

KE = mgh
KE = 0.15kg*9.8m/s^2*20.0m
KE = 29 J

The ball initially had 29 J of kinetic energy

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Driving home from school one day, you spot a ball rolling out into the street (Figure 5-21). You brake for 1.20 s, slowing your 950-kg car from 16.0 m/s to 9.50 m/s.a) What was the average force exerted on your car during braking?
b) How far did you travel while braking?

Answers

a ) v = v o + a t  ( the acceleration will be negative )
9.50 = 16.0 + a * 1.2
a * 1.2 = -16.0 + 9.50
a * 1.2 = - 6.5 
a = - 6.5 : 1.2
a = - 5.4167 m/s²
F = m * a = 950 kg * 5.4167 m/s²
F = 5,145.8 N ( the average force exerted on a car during braking )
b ) d = v o - a t² / 2
d = 16.0 * 1.2 - ( 5.4167 * 1.2² / 2 ) =
= 19.20 - 3.90 = 15.30 m

How are moving pulleys different from fixed-position pulleys? (Points : 3) Moving pulleys have more force than fixed-position pulleys. Moving pulleys are easier to use than fixed-position pulleys. Moving pulleys are attached to the object and move with the object. Fixed-position pulleys are connected to a fixed point and do not move. Moving pulleys are attached to the object and are stationary. Fixed-position pulleys are connected to a fixed point and move freely.

Answers

Answer : Option D) Fixed-position pulleys are connected to a fixed point and do not move.

Explanation : As the name suggests the moving pulleys move freely whereas the fixed pulleys as per their name is attached to a fixed position and at a fixed point and they can not move freely.

Movable pulleys are ones which has one part of the rope attached to a fixed object, like a bar or a beam. Whereas when both the parts of a rope are attached to a fixed object, this is called as a fixed pulley.

"Fixed-position pulleys are connected to a fixed point and do not move" is the one among the following choices given in the question that explains how the moving pulleys are different from fixed-position pulleys. The correct option among all the options that are given in the question is the fourth option.

A scientist is conducting research to determine how much pressure a dam can withstand. Why are good observations important to his research?

Answers

The things that a scientist should consider while observing the force is the environmental conditions,the force that is expected to act on the dam, the means to contain that force,  and compare different types of designs in accordance with the location of the dam

Just as the skydiver steps out of the helicopter Somos what do you start a stopwatch so the time is zero at the skydiver steps out of the plane what is the skydivers dour velocity at the instant just before starting to fall

Answers

The same as that of the aircraft that he /she is in. If flying level, it would be zero.

The Hubble telescope’s orbit is 5.6 × 105 meters above Earth’s surface. The telescope has a mass of 1.1 × 104 kilograms. Earth exerts a gravitational force of 9.1 × 104 newtons on the telescope. The magnitude of Earth’s gravitational field strength at this location is

Answers


Gravitational force = 9.1 x 10⁴ newtons

Mass  =  1.1 x 10⁴ kilograms

Gravitational field strength =  9.1 x 10⁴ newtons / 1.1 x 10⁴ kilograms

                                      =  ( 9.1 / 1.1)  (newton / kilogram)

                                       =   8.3 newton/kg

                                       or  8.3 m/s² .

One consequence of Einstein's theory of special relativity is that mass is a form of energy. This mass-energy relationship is perhaps the most famous of all physics equations: E=mc2,
where m is mass, c is the speed of the light, and E is the energy. In SI units, the units of speed are m/s. For the preceding equation to have consistent units (the same units on both sides of the equation), the units of E must be which of the following?

Answers

Answer:

Unit of energy is kg-m/s or Joules.

Explanation:

The mass- energy relationship in physics is given by :

E=mc^2

Where

m is the mass of the object

c is the speed of light

The SI unit of m is kilogram while the SI unit of c is as same as speed of light i.e. m/s. So, the unit of energy is kg-m/s. It is also equivalent to Joules.

So, the SI unit of energy is kg-m/s or Joules. Hence, this is the required solution.

Joule is the si unit for energy