Conservation of mechanical energy — NEET & JEE Questions

Question 1 · difficulty L1 · recall

When only conservative forces do work, the total mechanical energy

• A. remains constant
• B. always increases
• C. always decreases
• D. is always zero

Question 2 · difficulty L2 · understanding

Mechanical energy is the sum of

• A. kinetic and potential energy
• B. heat and temperature
• C. mass and momentum
• D. force and acceleration

Question 3 · difficulty L2 · understanding

If non-conservative friction does negative work on a system, mechanical energy generally

• A. decreases
• B. increases
• C. remains exactly constant
• D. becomes infinite

Question 4 · difficulty L2 · understanding

For a freely falling body neglecting air resistance, as height decreases

• A. potential energy decreases while kinetic energy increases
• B. both potential and kinetic energy decrease
• C. both remain constant separately
• D. kinetic energy decreases

Question 5 · difficulty L3 · application

A 2 kg body is dropped from height 5 m. Neglect air resistance and take g = 10 m/s². Its kinetic energy just before hitting the ground is

• A. 100 J
• B. 50 J
• C. 10 J
• D. 200 J

Question 6 · difficulty L3 · application

A frictionless roller coaster descends by 20 m. The increase in speed satisfies

• A. $v^2-u^2=2g(20)$
• B. $v-u=g(20)$
• C. $v^2-u^2=g/20$
• D. $v=u$

Question 7 · difficulty L3 · application

A spring stores 8 J of energy and launches a 1 kg block on a frictionless surface. If all spring energy becomes kinetic, the block speed is

• A. 4 m/s
• B. 2 m/s
• C. 8 m/s
• D. 16 m/s

Question 8 · difficulty L3 · application

A pendulum bob is released from rest at a height h above its lowest point. Neglecting losses, its speed at the bottom is

• A. $\sqrt{2gh}$
• B. $gh$
• C. $\sqrt{gh}$
• D. $2gh$

Question 9 · difficulty L4 · application

A 1 kg block slides down a frictionless track from rest through a vertical drop of 10 m. Taking g = 10 m/s², its speed at the bottom is closest to

• A. 14.1 m/s
• B. 10 m/s
• C. 20 m/s
• D. 5 m/s

Question 10 · difficulty L4 · application

A block starts with 50 J of mechanical energy and friction does -15 J of work. What is its final mechanical energy?

• A. 35 J
• B. 50 J
• C. 65 J
• D. 15 J