An object is shot from the back of a truck moving at 40 km/h on a straight horizontal road. The launcher is aimed upward, perpendicular to the bed of the truck. If air resistance is neglected, the object will fall:
a. depends on the value of g
b. in front of the truck
c. depends on the initial speed of the object
d. on the truck
e. behind the truck
What do you think? Hint: The object leaves the truck bed with the same horizontal velocity component as the truck.
OR: Consider what happens as seen from the inertial coordinate system of the truck. The object goes straight up and comes straight down.
To determine where the object will fall, we need to consider the motion of the object relative to the motion of the truck.
When the object is shot from the back of the truck, it has two separate components of motion:
1. The horizontal motion, which is the same as the motion of the truck, moving at 40 km/h.
2. The vertical motion, influenced by gravity.
Because air resistance is neglected, there are no horizontal forces acting on the object. Therefore, the horizontal speed of the object will remain constant at 40 km/h.
Now, let's consider the vertical motion. If the object is shot straight up with a certain initial speed, it will slow down due to the force of gravity, eventually reaching its maximum height and then falling back down.
Since the gravity pulls the object downwards, it will continue to move vertically against the horizontal motion of the truck. As a result, the object will fall:
e. behind the truck
Therefore, the correct answer is e. behind the truck.