NEET Laws of Motion — Set 1

Question 1

A book of mass $ 2 \, \text{kg} $ is at rest on a horizontal table. What is the magnitude of the normal force exerted by the table on the book? (Take $ g = 10 \, \text{m/s}^2 $)

Accepted Answer

The book is at rest, so the net force on it must be zero by Newton’s First Law. The weight of the book acts downward and is given by $ mg = 2 \times 10 = 20 \, \text{N} $. The normal force $ R $ acts upward and balances the weight. Thus, $ R = mg = 20 \, \text{N} $.

Question 2

A $ 0.6 \, \text{kg} $ stone in a vertical circle of radius $ 1.5 \, \text{m} $ has a tension of $ 20 \, \text{N} $ at the bottom. What is the tension at the top? (Take $ g = 10 \, \text{m/s}^2 $)

Accepted Answer

Bottom: $ T_b - mg = m \omega^2 r \Rightarrow 20 - 0.6 \times 10 = 0.6 \times \omega^2 \times 1.5 $. $ 20 - 6 = 0.9 \omega^2 \Rightarrow 14 = 0.9 \omega^2 \Rightarrow \omega^2 = \frac{14}{0.9} \approx 15.56 $. Top: $ T_t + mg = m \omega^2 r \Rightarrow T_t + 0.6 \times 10 = 0.6 \times 15.56 \times 1.5 $. $ T_t + 6 = 14 \Rightarrow T_t = 14 - 6 = 8 \, \text{N} $.

Question 3

A $ 10 \, \text{kg} $ mass in a lift accelerating upward at $ 3 \, \text{m/s}^2 $ is pushed downward with a force of $ 50 \, \text{N} $ by a spring. What is the normal force on the floor? (Take $ g = 10 \, \text{m/s}^2 $)

Accepted Answer

Net force on mass: $ N - mg - F_{\text{spring}} = ma $. $ N - 10 \times 10 - 50 = 10 \times 3 $. $ N - 100 - 50 = 30 $. $ N - 150 = 30 \Rightarrow N = 180 \, \text{N} $.

NEET Physics: Laws of Motion — Practice Set 1

Q1. A book of mass \( 2 \, \text{kg} \) is at rest on a horizontal table. What is the magnitude of the normal force exerted by the table on the book? (Take \( g = 10 \, \text{m/s}^2 \))

Q2. A \( 0.6 \, \text{kg} \) stone in a vertical circle of radius \( 1.5 \, \text{m} \) has a tension of \( 20 \, \text{N} \) at the bottom. What is the tension at the top? (Take \( g = 10 \, \text{m/s}^2 \))

Q3. A \( 10 \, \text{kg} \) mass in a lift accelerating upward at \( 3 \, \text{m/s}^2 \) is pushed downward with a force of \( 50 \, \text{N} \) by a spring. What is the normal force on the floor? (Take \( g = 10 \, \text{m/s}^2 \))

Q5. A \( 4.8 \, \text{kg} \) block on a \( 37^\circ \) incline (\( \mu_k = 0.2 \)) is pulled upward by a \( 6.8 \, \text{kg} \) mass over a pulley. What is the tension? (Take \( g = 10 \, \text{m/s}^2 \), \( \sin 37^\circ = 0.6 \), \( \cos 37^\circ = 0.8 \))

Q6. A force of \( 10 \, \text{N} \) acts on a body of mass \( 2 \, \text{kg} \) initially at rest. What is the velocity of the body after \( 5 \, \text{s} \)?

Q7. A \( 3000 \, \text{kg} \) truck accelerates at \( 3 \, \text{m/s}^2 \) for \( 4 \, \text{s} \), then a \( 2 \, \text{kg} \) ball is dropped. What is the horizontal distance traveled by the ball in \( 2 \, \text{s} \) relative to the ground? (Neglect air resistance)

Q9. A man of mass \( 60 \, \text{kg} \) stands on a weighing scale in a lift moving upwards with an acceleration of \( 2 \, \text{m/s}^2 \). What is the reading on the scale? (Take \( g = 10 \, \text{m/s}^2 \))

Q10. A \( 0.15 \, \text{kg} \) ball moving at \( 25 \, \text{m/s} \) at \( 60^\circ \) to a wall rebounds at \( 30^\circ \) with the same speed. What is the impulse magnitude? (Take \( \sin 60^\circ = 0.866 \), \( \cos 60^\circ = 0.5 \), \( \sin 30^\circ = 0.5 \), \( \cos 30^\circ = 0.866 \))

Q11. A batsman hits a ball of mass \( 0.2 \, \text{kg} \) coming at \( 15 \, \text{m/s} \) straight back with the same speed. What is the impulse imparted to the ball?

Q12. A \( 4 \, \text{kg} \) block on a horizontal surface (\( \mu_k = 0.3 \)) is connected to a \( 6 \, \text{kg} \) mass over a pulley. A \( 12 \, \text{N} \) force opposes the \( 4 \, \text{kg} \) block. What is the acceleration? (Take \( g = 10 \, \text{m/s}^2 \))

Q13. A \( 0.32 \, \text{kg} \) stone is whirled in a horizontal circle of radius \( 1.5 \, \text{m} \) at \( 48 \, \text{rev/min} \). What is the tension? (Take \( g = 10 \, \text{m/s}^2 \))

Q14. A \( 7.4 \, \text{kg} \) block on a \( 53^\circ \) incline (\( \mu_k = 0.15 \)) is pulled upward by a \( 9.4 \, \text{kg} \) mass over a pulley. What is the acceleration? (Take \( g = 10 \, \text{m/s}^2 \), \( \sin 53^\circ = 0.8 \), \( \cos 53^\circ = 0.6 \))

Q15. A \( 2000 \, \text{kg} \) truck accelerates at \( 2 \, \text{m/s}^2 \) for \( 5 \, \text{s} \), then a \( 1 \, \text{kg} \) ball is dropped. What is the horizontal distance from the drop point after \( 1.5 \, \text{s} \)? (Neglect air resistance)