Homework Help: physics (mechanics)

Posted by andrew on Thursday, April 12, 2012 at 11:20am.

A running man has half the kinetic energy of a boy half his mass. The man speeds up by 1.30 m/s and then has the same kinetic energy as the boy. What is the speed (in meters/second) of the boy?

physics (mechanics) - Steve, Thursday, April 12, 2012 at 11:41am
man velocity: x
boy velocity: b
1/2 (2m)x^2 = 1/2 * 1/2 my^2
4x^2 = y^2

1/2 (2m)(x+1.3)^2 = 1/2 my^2
2(x+1.3)^2 = 4x^2
x^2 + 2.6x + 1.69 = 2x^2
x^2 - 2.6x - 1.69 = 0
x = 3.138

check:
1/2 (2m)*3.138^2 = 1/2 * 1/2 m*6.276^2
9.847 = 1/2 * 19.694 = 9.847

1/2 (2m)*4.438^2 = 1/2 m*6.276^2
19.694 = 19.694

Answer this Question

Related Questions

science - A running man has half the kinetic energy of that of a boy of half of ...
physics - A father racing his son has half the kinetic energy of the son, who ...
Physics - A man of mass 75.5 kg walks down the aisle of an airplane at a speed ...
Physics (algebra bit) - I do not see how to do this problem One car has twice ...
AMHS'Mechanics - The spring shown in figure is unstreched when a man starts ...
Physics - A boy has a mass of 45 kg and is running with a velocity of 8 m/s. ...
physics - A racing dog is initially running at 20.0 , but is slowing down. Q1. ...
physics - A racing dog is initially running at 15.0 m/s, but is slowing down.How...
Intergated chemistry/physics - A 200 man is running 3 miles per hour and ...
physics - A man jogs at a spee of 1.1 m/s. His dog waits 1.6s and then takes off...

For Further Reading

First Name:
School Subject:
Answer: