Question

a machine rated as 150w changes the velocity of a 10kg mass from 4ms to 10ms in 4s the efficiency of the machine is nearly​

Answer 1

Explanation:

mass = 10 kg, v = 10 m/s, u = 4 m/s

acceleration = (10 - 4)/4 = 1.5 m/s^2

force = 10*1.5 = 15 N

displacement

s = (10^2 - 4^2)/(2*1.5) = 84/3 = 28 m

work done in moving the object

= force*displacement

= 15*28 = 420 joules

power required = rate of work done

= 420/4 = 105 watts

efficiency =required power/rated power

= 105/150 = 0.7 = 70 %

Answer 2

$\bold{Solution\::}$

Kinetic energy = 1/2 mv²

But we have given that final velocity is 10 m/s and initial velocity is 4 m/s.

So,

Kinetic energy = 1/2m (vf² - vi2)

Here..

• vf = final velocity
• vi = initial velocity

Mass = 10 kg

Substitute the known values in above formula

=> 1/2 × 10[(10)² - (4)²]

=> 5 (100 - 16)

=> 420 J

Now,

Power delivered = Work/Time

=> 420/4

=> 105 W

Now,

Efficiency = Power delivered/Power rating × 100

=> 105/150 × 100

=> 0.7 × 100

=> 70%

•°• Efficiency of the machine is 70%