Finding initial kinetic energy

In summary, the student is trying to find the initial kinetic energy of a 0.22kg rock thrown horizontally at 20.0m/s from a height of 10.0m, ignoring air resistance. Using the equation Ek = mv^2/2, the student simplifies the problem and plugs in the known values, getting an answer of 9.68J. However, the correct answer is 44J, suggesting a mistake in the calculation process. The student is advised to check their arithmetic and pay attention to the order of operations.
  • #1
DPXJube
12
0

Homework Statement


A student throws 0.22kg rock horizontally at 20.0m/s from 10.0m above the ground. Ignore air resistance.

Find the initial kinetic energy of the rock


Homework Equations


Ek = mv^2/2


The Attempt at a Solution


This sounds INCREDIBLY easy and every shape or form
Simplying plugging in what I know

Ek =(0.22)(20.0)^2/2

Get's me the answer of 9.68
However APPARENTLY that's the wrong answer
The answer that I'm given is 44J
How is this possible? I must have gone completely off track somewhere.
 
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  • #2
Check your arithmetic. Pay careful attention to the order of operations.
 
  • #3
DPXJube said:

Homework Statement


A student throws 0.22kg rock horizontally at 20.0m/s from 10.0m above the ground. Ignore air resistance.

Find the initial kinetic energy of the rock

Homework Equations


Ek = mv^2/2

The Attempt at a Solution


This sounds INCREDIBLY easy and every shape or form
Simplying plugging in what I know

Ek =(0.22)(20.0)^2/2

Get's me the answer of 9.68
However APPARENTLY that's the wrong answer
The answer that I'm given is 44J
How is this possible? I must have gone completely off track somewhere.

Your (red) statement is correct - if clumsily written - it would appear the only problem is when you start entering the numbers into your calculator - not that you should need one for that calculation.
 

What is initial kinetic energy?

Initial kinetic energy is the amount of energy possessed by an object due to its motion at the beginning of a particular time period. It is a measure of the object's ability to do work as a result of its motion.

How do you calculate initial kinetic energy?

The formula for calculating initial kinetic energy is E = 1/2 * m * v^2, where E is the kinetic energy, m is the mass of the object, and v is the velocity of the object. The unit of measurement for kinetic energy is Joules (J).

What is the difference between initial and final kinetic energy?

Initial kinetic energy refers to the energy possessed by an object at the beginning of a particular time period, while final kinetic energy refers to the energy possessed by the object at the end of the same time period. The difference between the two is the change in kinetic energy during that time period.

What factors affect initial kinetic energy?

The two main factors that affect initial kinetic energy are the mass and velocity of the object. A heavier object or a faster moving object will have a higher initial kinetic energy compared to a lighter or slower object, respectively.

Why is it important to find initial kinetic energy?

Finding initial kinetic energy is important in many scientific and engineering fields. It allows us to understand the energy involved in an object's motion and how it can be used to do work. It is also essential in determining the behavior and performance of moving objects, such as in designing vehicles or analyzing sports movements.

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