A cart of mass 20kg rolls with negligible friction down its track. At point A its speed is 4m/s. If point A is 5m higher than point b, what is its kinetic energy at point B?

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Answer 1 · 2016-06-14T08:19:01

#v_B=10.7" "m/s#

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#"An object at on the point A has a Potential energy with respect to the ground"#

#"The potential energy of an object is directly proportional with its height from ground "#

#"The Potential energy of its will change if The object goes to from A to B" #

#Delta E_p=m*g(h_A-h_B)#

#E_p " Represents the change of potential energy of object"#

#"Plug " m=20 " "kg" ; "g=9.81" "m/s^2" ; "h_A-h_B=5" "m#

#E_p=20*9.81*5=100*9.81=981" "J#

#"The Potential energy of object has decreased ."#

#"The kinetic energy and velocity of object will have increased"#

#"The kinetic energy of object at on the point of A is:"#

#E_A=1/2*m*v^2 " ; plug m=20 ; kg v=4 " m/s^2#

#E_A=1/2*20*4^2" ; "E_A=10*16=160 " "J#

#"The kinetic energy of object at on the point B is:"#

#E_B=160+981=1141J#

#so" " E_k=1/2*m*v^2#

#1141=1/2*m*v_B^2#

#1141=1/2*20*v_B^2#

#114.1=v_B^2#

#sqrt(v_B^2)=sqrt(114.1)#

#v_B=10.7" "m/s#