Question

an object of mass 5kg accelerates from 4m/s to 8m/s in 4s.how much work is done on it?​

Answer 1

Given :-

★ Mass, m = 5 kg

★ Time, t = 4 sec

★ Accelerates from 4m/s to 8m/s in 4s.

Therefore ,

∆ v = (8-4) m/s

= 4 m/s

To Find :-

★ Work down ( W)

Solution :-

We need to use Newton's second law to find F.

$\boxed{\rm F = ma}$

Here, we know ____

a ( Acceleration ) is the rate of change velocity.

⟹ a = 4 /4 m/s²

⟹ a = 1 m/s²

Now, put the value of a in F = ma

F = ma

⟹ F = 5 × 1 N

⟹ F = 5 N

Now, we need to use laws of motion to find S.

Hence,

v² = u² + 2as

⟹ ( 8)² = (4)² + 2 ×1 s

⟹ s = 24 m

We know,

☞ Work down, W = F s

Note :-

The work down force is in the direction of S.

Substituting the values, we get ___

W = 24 × 5 J

⟹ W = 120 J

Hence,

work down is = 120J

Answer 2

Given :-

★ Mass, m = 5 kg

★ Time, t = 4 sec

★ Accelerates from 4m/s to 8m/s in 4s.

Therefore ,

∆ v = (8-4) m/s

= 4 m/s

To Find :-

★ Work down ( W)

Solution :-

We need to use Newton's second law to find F.

\boxed{\rm F = ma}

F=ma

Here, we know ____

a ( Acceleration ) is the rate of change velocity.

⟹ a = 4 /4 m/s²

⟹ a = 1 m/s²

Now, put the value of a in F = ma

F = ma

⟹ F = 5 × 1 N

⟹ F = 5 N

Now, we need to use laws of motion to find S.

Hence,

v² = u² + 2as

⟹ ( 8)² = (4)² + 2 ×1 s

⟹ s = 24 m

We know,

☞ Work down, W = F s

Note :-

The work down force is in the direction of S.

Substituting the values, we get ___

W = 24 × 5 J

⟹ W = 120 J

Hence,

work down is = 120J