Free Fall and Acceleration Due to Gravity (g) - UNSOLVED PRACTICE SET
Chapter: Gravitation | Topic: Free Fall and Acceleration g
FREE FALL AND ACCELERATION DUE TO GRAVITY (G) - UNSOLVED PRACTICE SET
Topic: Free Fall and Acceleration g
Multiple Choice Questions
Q1. When an object falls freely under gravity (ignoring air resistance), its:
- Velocity remains constant
- Acceleration remains constant but velocity increases
- Both velocity and acceleration increase with time
- Acceleration is zero because gravity balances air resistance
Q2. The value of acceleration due to gravity (g) at the Earth's surface is approximately:
- 6.674 × 10⁻¹¹ m/s²
- 9.8 m/s²
- 10 m/s² everywhere in the universe
- 9.8 km/s²
Q3. A stone is dropped from the top of a building. If we ignore air resistance, which of the following is true?
- It falls with constant speed
- It accelerates at 9.8 m/s² downward throughout the fall
- It decelerates as it approaches the ground
- Its acceleration depends on its mass
Q4. Astronauts inside a spaceship orbiting the Earth appear to be 'weightless'. This is because:
- There is no gravity in space
- The spaceship and astronauts are both in a state of free fall around the Earth
- The astronauts have zero mass in space
- Air resistance is absent in space
Q5. If a metal ball and a feather are dropped simultaneously in a vacuum, they will:
- Fall at the same rate and reach the ground together
- The metal ball reaches first because it is heavier
- The feather reaches first because it is lighter
- Neither falls because there is no air support
Q6. The equations of motion under free fall are the same as those for uniform acceleration, but with acceleration a replaced by g. If an object is thrown upward with initial velocity u, at the highest point its velocity is:
- u (same as the initial velocity)
- 2u
- Zero
- g
Short Answer Questions
Q7. Define 'free fall'. Is an object attached to a parachute in free fall? Why or why not?
Q8. Why does a heavy stone and a light pebble dropped from the same height (in vacuum) hit the ground at the same time? Many students find this confusing — explain it clearly.
Q9. How does the value of g change as you go:
(i) higher above the Earth's surface, and
(ii) deeper inside the Earth? Write one sentence for each.
Q10. During a cricket match in Bengaluru, a ball is hit straight up. Describe the ball's acceleration (magnitude and direction) during its upward journey, at the top, and during its downward journey.
Q11. Galileo dropped objects from the Leaning Tower of Pisa (according to popular legend). What was his key discovery, and why was it revolutionary for its time?
Q12. Write the three equations of uniformly accelerated motion. Then rewrite them specifically for a freely falling object, replacing 'a' with 'g' and 'displacement' with 'h' (height).
Long Answer Questions
Q13. Explain in detail what happens when you throw a ball vertically upward. Describe:
(i) its motion on the way up,
(ii) its state at the maximum height,
(iii) its motion on the way down, and
(iv) whether the acceleration changes direction at any point. Use the concept of free fall and the value of g in your explanation.
Q14. A student asks: 'If gravity pulls everything downward, why does a satellite not fall to Earth?' Using your knowledge of free fall and orbital motion, answer this question. Explain how a circular orbit is essentially a continuous free fall. You may use a simple diagram description.
Q15. Compare free fall on the Earth and free fall on the Moon. Given that the Moon's gravity is about 1/6th of Earth's, explain:
(i) how g is different on the Moon,
(ii) what would happen if you dropped a 5 kg stone on the Moon from the same height, and
(iii) what would you weigh on the Moon compared to Earth (in terms of g)?
Numerical / Application-Based Problems
Q16. A stone is dropped from a cliff and hits the ground after 4 seconds.
(i) What is the velocity of the stone just before hitting the ground?
(ii) What is the height of the cliff?
(iii) What would be the velocity after 2 seconds?
Q17. A ball is thrown vertically upward with an initial velocity of 19.6 m/s from the top of a building.
(i) How long does it take to reach the maximum height?
(ii) What is the maximum height reached above the throwing point?
(iii) At what time will it return to the same point?
Q18. An iron ball and a rubber ball, both of the same size, are dropped simultaneously from a height of 80 m in the school playground (not in vacuum — air resistance is present). The rubber ball takes longer to reach the ground.
(i) Which ball reaches first, and why?
(ii) If we performed the same experiment in a vacuum tube, what would happen? Explain.
(iii) Calculate the time taken by the iron ball (ignoring air resistance) using g = 10 m/s².