NEET Work Energy and Power — Set 11

Question 1

A force starts at $ 50 \, \text{N} $ over $ 6 \, \text{m} $, then decreases linearly to $ 10 \, \text{N} $ over $ 4 \, \text{m} $. What is the total work done?

Accepted Answer

Work in first part: $ W_1 = 50 \times 6 = 300 \, \text{J} $. Work in second part: $ W_2 = \frac{1}{2} (50 + 10) \times 4 = 30 \times 4 = 120 \, \text{J} $. Total work: $ W = 300 + 120 = 420 \, \text{J} $.

Question 2

A $ 1 \, \text{g} $ drop falls from $ 800 \, \text{m} $ and hits the ground at $ 30 \, \text{m/s} $. What is the work done by air resistance? (Take $ g = 10 \, \text{m/s}^2 $)

Accepted Answer

Work by gravity $ W_g = mgh = 0.001 \times 10 \times 800 = 8 \, \text{J} $. Final $ K = \frac{1}{2} \times 0.001 \times 30^2 = 0.45 \, \text{J} $. By work-energy theorem, $ K_f = W_g + W_r \Rightarrow 0.45 = 8 + W_r \Rightarrow W_r = -7.55 \, \text{J} $.

Question 3

A spring ($ k = 300 \, \text{N/m} $) is compressed by $ 0.2 \, \text{m} $. What is the potential energy stored?

Accepted Answer

Potential energy $ V = \frac{1}{2} k x^2 = \frac{1}{2} \times 300 \times (0.2)^2 = 150 \times 0.04 = 6 \, \text{J} $.

NEET Physics: Work Energy and Power — Practice Set 11

Q1. A force starts at \( 50 \, \text{N} \) over \( 6 \, \text{m} \), then decreases linearly to \( 10 \, \text{N} \) over \( 4 \, \text{m} \). What is the total work done?

Q2. A \( 1 \, \text{g} \) drop falls from \( 800 \, \text{m} \) and hits the ground at \( 30 \, \text{m/s} \). What is the work done by air resistance? (Take \( g = 10 \, \text{m/s}^2 \))

Q3. A spring (\( k = 300 \, \text{N/m} \)) is compressed by \( 0.2 \, \text{m} \). What is the potential energy stored?

Q4. A \( 10 \, \text{kg} \) block is pushed with \( 50 \, \text{N} \) over \( 8 \, \text{m} \) on a frictionless surface, starting from \( 1 \, \text{m/s} \). What is its final speed?

Q5. A motor lifts a \( 2000 \, \text{kg} \) load at \( 3.5 \, \text{m/s} \) against \( 4000 \, \text{N} \) friction. What is the power? (Take \( g = 10 \, \text{m/s}^2 \))

Q6. A \( 1.8 \, \text{kg} \) pendulum bob completes a vertical circle of radius \( 2 \, \text{m} \). What is the speed at the top? (Take \( g = 10 \, \text{m/s}^2 \))

Q7. A \( 45 \, \text{g} \) bullet at \( 1100 \, \text{m/s} \) emerges from a block with \( 50\% \) of its initial kinetic energy. What is its emergent speed?

Q8. A \( 10 \, \text{kg} \) mass is lifted \( 8 \, \text{m} \) in \( 5 \, \text{s} \) at constant speed. What is the power delivered? (Take \( g = 10 \, \text{m/s}^2 \))

Q9. A \( 12 \, \text{kg} \) block is pushed with \( 60 \, \text{N} \) over \( 5 \, \text{m} \) on a frictionless surface, starting from rest. What is its final speed?

Q10. A \( 0.9 \, \text{g} \) drop falls from \( 150 \, \text{m} \) and hits the ground at \( 13 \, \text{m/s} \). What is the work done by air resistance? (Take \( g = 10 \, \text{m/s}^2 \))