Name:
per:
pt hw 3.1
(linear) kinetic energy and wor
1.a. a bicycler has a mass of 80. kg. he pedals the bike 100 min 20 seconds. what is
his kinetic energy (ke; )?
given, unknown:
equation, substitute:
solution:
1.b. the bicycler (still 80.kg of mass) doubled his speed to 200m in 20 seconds, what
his new kinetic energy (ke)? what is the ratio of ke; and ke?
given, unknown:
solution
equation, substitute:
1.c. the bicycler doubled his speed. what happened to his ke?
2.a. car a has a mass of 250. kg. it's engine accelerates it from 0.0 to 20. m/s in 6.0
ndo (a) what is the car's acceleration in m s?
tio hstitute:
solution:

1.a) 1 kJ

1.b) 4 kJ

     ratio 1:4

1.c) 4 times as before

2.a)  3.33 m/s2

Explanation:

1.a) bicycle's velocity =Displacement/time

                                   =100/20 m/s

                                   =5 m/s

bicycler's KE =1/2 *mass*(velocity)^2

                      =1/2*80*5^2

                       =1000 J = 1 kJ

1.b) bicycle's new velocity =200/20 m/s

                                   =10 m/s

bicycler's new KE =1/2*80*10^2

                             =4000 J = 4 kJ

Ratio= KE 1 :KE new

        = 1 :4

1.c)  when bicycler's speed was doubled it increased the KE by 4 times (2^2). because In KE we consider the square of the speed , so the factor we increase the speed , the KE will get increased with the square value of it

ex : speed is triple the prior value , then the KE is as 3^2 times as before. that is 9 times

2.a) car acceleration = (20-0)/6 m/s2

                                  = 3.33 m/s2

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide