Question

1. Certain force acting on a 20 kg mass changes its velocity from
5 ms' to 2 m s! Calculate the work done by the force.​

Answer 1

Answer:

Kinetic energy is given by the expression, (E k) v = 1/2 mv^2

Where,

E k= Kinetic energy of the object moving with a velocity, v

(i) Kinetic energy when the object was moving with a velocity 5 m s-1

(E k)5 = 1/2 — 20 — (5)2 = 250 J

Kinetic energy when the object was moving with a velocity 2 m s-1

(E k)2 = (1 )/2x 20 — (2)2 = 40 J.

Answer 2

Hello :)

mass = 20 kg

initial velocity (u) = 5 m/sec

final velocity (v) = 2 m/sec

time (t)= 1sec

∴ v= u+ at

a= ( v- u) / t

a= ( 2 ms-¹ - 5 ms-¹) / 15

a= - 3 ms-²  

v²- u²= 2as

= ( 2ms -1 )² - ( 5ms-¹) ²

= 2× (-3ms-²) ×5

= -21 m²s² = -6ms-²× 5

= s = 7/2 metre

∴ workdone= f × s

F = m× a

 work = m× a× s

= 20 kg × ( -3ms-²) × 7/2m

= - 210 joules.

hope it helps!!!

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