Learning goal: to practice problem-solving strategy 4.1 for projectile motion problems. a rock thrown with speed 12.0 m/s and launch angle 30.0 ∘ (above the horizontal) travels a horizontal distance of d = 15.5 m before hitting the ground. from what height was the rock thrown? use the value g = 9.800 m/s2 for the free-fall acceleration.

The height from which the rock was thrown is 1.92 m

Solution:

As per the question:

Speed with which the rock is thrown, v = 12.0 m/s

Horizontal distance traveled by the rock before it hits the ground, d = 15.5 m

Launch angle,

Now,

To calculate the height, h from which the rock was thrown:

First, since we consider the horizontal motion in the trajectory of the rock, thus the time taken is given by:

Now,

The height from which the rock was thrown is given by the kinematic eqn, acceleration in the horizontal direction is zero:

the height was thrown = 1.938 m

Explanation:

given,

speed of the rock = 12 m/s

angle of launch = 30.0 ∘

horizontal distance = d = 15.5 m

acceleration due to gravity  = 9.8 m/s²

t = 1.49 s

hence, the height was thrown = 1.938 m

force tends to be low and long diustance masses are high