The speed of the pendulum at its highest point is zero. As it starts to move downwards, the speed increases and reaches the maximum when it is at its lowest point. This gives the pendulum the maximum kinetic energy at the lowest point. Also, its potential energy is zero here. When the pendulum starts to climb up again, the kinetic energy is converted to potential energy.
In the question, the pendulum has a highest point at a height of 1m. The acceleration due to the gravitational force of the Earth is g= 9.8 m/s^2.
Now we use these formula between distance travelled, speed and acceleration:
a = (v - u)/t
=> t = (v- u)/a
d = (1/2)(v + u)*t
=> d = (1/2)(v + u)(v - u) / a
=> d = (v^2 - u^2) / 2a
=> v^2 = 2ad + u^2
Now we have d = 1 m , u = 0 m/s , a = 9.8 m/s^2. Substituting these values in the formula gives us:
v^2 = 2* 1* 9.8 + 0
=> v = sqrt ( 19.6)
=> v = 4.427 m/s
Therefore the required speed at the lowest point is 4.427 m/s.