When a ball is thrown vertically upwards, the initial velocity is positive and the acceleration due to gravity is negative. The velocity and acceleration can be determined using the following equations:
For velocity: v = u + at
For displacement: s = ut + (1/2)at^2
Where: v = final velocity u = initial velocity a = acceleration t = time s = displacement
Given: Initial velocity (u) = 15 m/s (positive) Time (t) = 2 s
To find the velocity at 2 seconds, we can use the equation:
v = u + at
Substituting the known values:
v = 15 + (-9.8 * 2) v = 15 - 19.6 v = -4.6 m/s
Therefore, the velocity of the ball at 2 seconds is approximately -4.6 m/s. The negative sign indicates that the ball is moving in the opposite direction, i.e., upwards.
To find the acceleration at 2 seconds, we know that the acceleration due to gravity (g) is approximately -9.8 m/s². Therefore, the acceleration remains constant throughout:
a = -9.8 m/s²
Thus, the acceleration of the ball at 2 seconds is approximately -9.8 m/s².