Question #1c2bd

1 Answer
Apr 27, 2016

"4.4 J"4.4 J

Explanation:

Before the force is applied we know

"momentum" = "mass" times "velocity" = "10 kg m/s"momentum=mass×velocity=10 kg m/s

Since mass in the above is "5 kg"5 kg, then velocity = "2 ms"^(-1)2 ms1

We can now work out kinetic energy, KE:

KE=1/2mv^2=1/2*5*2^2="10 J"KE=12mv2=12522=10 J

The force of "0.2 N"0.2 N is now applied in the direction of travel for 1010 seconds. Newton's second law can be expressed as "the force applied equals the rate of change of momentum". OR

F=(mv-"mu")/t=m * (v-u)/tF=mvmut=mvut

Where vv is the final velocity after applying force, and uu is the initial velocity ( "2 ms"^(-1)2 ms1 in this case from above)

So

0.2 = 5 * ((v-2))/100.2=5(v2)10

rearranging helps us find vv

2 = 5 * (v-2)2=5(v2)

2/5 = v-225=v2

v = 12/5" ms"^(-1)v=125 ms1

Hence final kinetic energy, KEKE, is

KE = 1/2mv^2 = 1/2 * 5 * (12/5)^2 = "14.4 J"KE=12mv2=125(125)2=14.4 J

So the overall change in KEKE is

Delta_"KE" = 14.4 - 10 = "4.4 J"