A boy is sitting in a car moving with uniform velocity. The boy throws a ball vertically upwards which falls back into his hands. A man standing on the road watches the motion of the ball. The path of the motion of the ball will be:

Options

A. a straight line for the man
B. a straight line for the boy
C. a parabola for the man
D. a parabola for the boy

Answer

To solve the problem, we need to analyze the motion of the ball as seen by both the boy in the car and the man standing on the road.

### Step-by-step Solution:

1. **Understanding the Scenario**:
- The boy is sitting in a car that is moving with uniform velocity.
- He throws a ball vertically upwards.
- The ball returns to his hands.

2. **Analyzing the Boy's Perspective**:
- From the boy's perspective inside the car, the ball is thrown straight up and comes straight back down to his hands.
- Since the car is moving with a constant velocity, there are no horizontal forces acting on the ball from the boy's frame of reference.
- Thus, to the boy, the motion of the ball is a vertical line.

3. **Analyzing the Man's Perspective**:
- The man standing on the road observes the car moving horizontally with a constant velocity.
- When the boy throws the ball upwards, the ball also has the horizontal velocity of the car at the moment it is thrown.
- As the ball rises and falls, it continues to move horizontally with the same velocity as the car due to inertia.

4. **Path of the Ball as Seen by the Man**:
- The ball follows a combination of vertical and horizontal motion.
- While it goes up and comes down, it also moves horizontally with the car's velocity.
- Therefore, the path traced by the ball, as seen by the man on the road, will be a parabolic trajectory.

5. **Conclusion**:
- The boy sees the ball moving in a straight line (up and down).
- The man sees the ball moving in a parabolic path.
- Therefore, the answer is that the path of the motion of the ball will be a parabola as observed by the man on the road.

### Final Answer:
The path of the motion of the ball, as observed by the man standing on the road, will be a **parabola**.