Question

a spear of mass 4 kg is dropped from a certain height after 5 seconds it's kinetic energy=
a. 5J
b.50J
c.5kJ
d.50KJ​

Answer 1

Answer:

c

Step-by-step explanation:

velocity at time =0sec

v=u+at

v=0+10×5

v=50

velocity at time =5sec

KE=1/2mv²

KE=1/2×4×(50)²

KE=2×2500

KE=5000j=5Kj

Kinetic energy at time =5sec will be 5kj

Answer 2

Answer:

c)5kJ

Step-by-step explanation:

m=4kg

t=5sec

u=0 (object is dropped)

a=10m/s² (gravity)

v=u+at ( 1st equation of motion)

v=0+10*5=50m/s

K.E.=1/2mv²

     =1/2*4*50²

     =2*2500=5000J=5kJ (as 1kJ=1000J)