NEET Kinematics — Set 5

Question 1

A stone falls from a height $ h $ and covers $ 78.4 \, \text{m} $ in the last $ 2 \, \text{s} $ of its fall. What is the total time of fall? (Take $ g = 9.8 \, \text{m/s}^2 $)

Accepted Answer

Total time = $ t $, last 2 s: $ h = \frac{1}{2} \cdot 9.8 \cdot t^2 $, $ h - 78.4 = \frac{1}{2} \cdot 9.8 \cdot (t - 2)^2 $. Distance in last 2 s: $ 78.4 = 4.9 [t^2 - (t - 2)^2] \Rightarrow 16 = t^2 - (t^2 - 4t + 4) \Rightarrow 16 = 4t - 4 \Rightarrow t = 5 \, \text{s} $.

Question 2

A truck moves at a constant speed of $ 25 \, \text{m/s} $ for $ 20 \, \text{s} $. What is the distance covered?

Accepted Answer

For constant speed, distance $ x = v t $. Here, $ v = 25 \, \text{m/s} $, $ t = 20 \, \text{s} $. Substitute: $ x = 25 \cdot 20 = 500 \, \text{m} $. The distance covered is $ 500 \, \text{m} $.

Question 3

A ball is thrown upwards with a speed of $ 60 \, \text{m/s} $. What is the time to reach the maximum height? (Take $ g = 10 \, \text{m/s}^2 $)

Accepted Answer

At max height, $ v = 0 $. Use $ v = v_0 + a t $. Here, $ v_0 = 60 \, \text{m/s} $, $ a = -10 \, \text{m/s}^2 $. Substitute: $ 0 = 60 - 10 t \Rightarrow 10 t = 60 \Rightarrow t = 6 \, \text{s} $. The time taken is $ 6 \, \text{s} $.

NEET Physics: Kinematics — Practice Set 5

Q1. A stone falls from a height \( h \) and covers \( 78.4 \, \text{m} \) in the last \( 2 \, \text{s} \) of its fall. What is the total time of fall? (Take \( g = 9.8 \, \text{m/s}^2 \))

Q2. A truck moves at a constant speed of \( 25 \, \text{m/s} \) for \( 20 \, \text{s} \). What is the distance covered?

Q3. A ball is thrown upwards with a speed of \( 60 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))

Q4. A ball is thrown upwards with a speed of \( 42 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))

Q5. A ball is thrown upwards with a speed of \( 52 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))

Q6. A cyclist moves at a constant speed of \( 7 \, \text{m/s} \) for \( 60 \, \text{s} \). What is the distance covered?

Q7. A ball is thrown upwards at \( 15 \, \text{m/s} \) from a \( 45 \, \text{m} \) tower. What is its speed when it passes \( 15 \, \text{m} \) below the tower’s top? (Take \( g = 10 \, \text{m/s}^2 \))

Q8. A car moving at \( 30 \, \text{m/s} \) decelerates uniformly to rest in \( 6 \, \text{s} \). What is the distance covered?

Q9. A cyclist moves at a constant speed of \( 9 \, \text{km/h} \) for \( 20 \, \text{minutes} \). What is the distance covered?

Q10. A car moving at \( 72 \, \text{km/h} \) decelerates uniformly and stops in \( 8 \, \text{s} \). What is the magnitude of deceleration?