Question

1 kg ball thrown up with speed of 9.9m/s . Calculate the work done by its weight in one second.? ​

Answer 1

✰ Question ✰

⋄ 1 kg ball thrown up with speed of 9.9m/s . Calculate the work done by its weight in one second.?

___________________

✰Given:-

⋄ Mass of ball =1 kg

⋄ Initial velocity of ball (u) = 9.9m/s

⋄ Acceleration due to gravity (g) = 9.8m/s²

⋄ Time taken (t) = 1 s

✰To Find :-

⋄ Work done by its weight???

✰Solution :-

➧ The distance moved in One second is

$s = ut + \frac{1}{2} gt {}^{2} \\ \\ s = 9.9 \times 1 + \frac{1}{2} \times 9.8 \times 1 {}^{2} \\ \\ s = 5m$

The weight of the ball is (mg) = 1×9.8 =9.8 N in the downward direction.

➧ Work done in one second = (-9.8)×5=-49J.

∴The work done by its weight is -49 J.

Answer 2

Given : a 1 kg ball is thrown upwards with a speed of 9.9 m/s

To Find : calculate the work done by its Weight in one second​

Solution:

Initial Velocity = 9.9 m/s

a =  g = - 9.8 m/s

V = U + at

Velocity after 1 sec =   9.9 + (-9.8)(1)

= 0.1  m/s

KE = Kinetic Energy

KE   = (1/2)mV²

KE at initial  =  (1/2)*1(9.9)²

KE after 1 sec =  (1/2)*1(0.1)²

Change in KE  =  (1/2)*1(0.1)² -  (1/2)*1(9.9)²

= (1/2) ( 0.1 + 9.9)(0.1 -9.9)

= (1/2)(10)(-9.8)

= -49 J

Work Done  = -49 J

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