Question

What is the work done that must be done to stop a lorry of mass 4000kg moving at a velocity of 54km/hr in 2s. ( Class 11 - Work, Energy and Power )
**Detailed Answers Please**​

Answer 1

Given:-

• Mass of lorry (m) = 4000Kg

• Final velocity of lorry (v) = 0m/s

• Initial velocity of lorry (u) = 54km/h = 54×5/18= 15m/s

• Time Taken = 2s.

To Find:-

• Work done to stop lorry (W).

Solution:-

Firstly we calculate acceleration of the lorry

By using this formula

⟹ a = v-u/t

Put the value, we get

⟹ a = 0-15/2

⟹ a = -7.5m/s²

here negative sign show deceleration

∴ The acceleration of the lorry is 7.5m/s²

And, we know that

By using this formula

⟹ S= ut +1/2at².

⟹ S = 15×2+1/2×(-7.5)×2²

⟹ S = 30 + 1/2 × (-7.5) × 4

⟹ S = 30-15

⟹ S = 15m

∴ The displacement of the lorry is 15m

Calculating the Force

⟹. Force = Mass×Acceleration

Put the value , we get

⟹ Force = 4000× 7.5

⟹ Force = 30000 N

∴ The force applied on the lorry is 300000 Newton.

And now , we calculate the work done

⟹ Work done = Force × displacement

⟹ W = F×d

Put the value, we get

⟹ W = 30000 × 15

⟹ W = 450000

⟹ W = 45×10⁴ Joule

∴ The Work done to stop the lorry is 45×10⁴ Joule.

Answer 2

Answer:

plz refer above answer...................................