A body starting from rest moves with uniform acceleration until it attains a speed of 100m/s after 20 s. It maintained this speed for the next 30s and came to rest by  uniformly deceleration in 30s. (a.) Find its acceleration.

Asynthetic fiber used in manufacturing carpet has tensile strength that is normally distributed with mean 75.5 psi and standard deviation 3.5 psi. how is the standard deviation of the sample mean changed when the sample size is increased from n equals 8 to n equals 47