Answer:
Explanation:
Given:
[tex]mass\ (m)=2000\ kg[/tex]
[tex]initial\ velocity\ (v_o)=90\ km/h[/tex]
[tex]=(90\times1000\div3600)\ m/s[/tex]
[tex]=25\ m/s[/tex]
[tex]final\ velocity\ (v)=72\ km/h[/tex]
[tex]=(72\times1000\div3600)\ m/s[/tex]
[tex]=20\ m/s[/tex]
[tex]\boxed{kinetic\ energy\ (KE)=\frac{1}{2}mv^2 }[/tex]
(a) Initial KE:
[tex]KE_o=\frac{1}{2} mv_o^2[/tex]
[tex]=\frac{1}{2} (2000)(25)^2[/tex]
[tex]=625,000\ J[/tex]
(b) Final KE:
[tex]KE=\frac{1}{2} mv^2[/tex]
[tex]=\frac{1}{2} (2000)(20)^2[/tex]
[tex]=400,000\ J[/tex]
(c) Change in KE
[tex]\Delta KE=KE-KE_o[/tex]
[tex]=400,000-625,000[/tex]
[tex]=-225,000\ J[/tex]
