1. a crane lifts a 75kg mass a height of 8 m. calculate the gravitational potential energy
gained by the mass:

GP.E = 5880 j

Explanation:

Given data:

Mass = 75 kg

height = 8 m

Potential energy = ?

Solution:

The formula for gravitational potential energy is

GPE = mgh

m = mass in kilogram

g = acceleration due to gravity

h = height in meter above the ground

Formula:

GP.E = mgh

Now we will put the values in formula.

g = 9.8 m/s²

GP.E = 75 Kg × 9.8 m/s²× 8 m

GP.E = 5880 Kg.m²/s²

Kg.m²/s² = j

GP.E = 5880 j

Answer; A
It is best to say that the protection to properties offered by sea walls along coasts decreases the present and future risk to human properties. 

Explanation;
Seawalls are vertical walls that are constructed on the sea shores to prevent upland erosion and storm surge flooding. They are massive concrete structures emplaced along a stretch of shoreline mostly at urban beaches. These structures decrease the present and future risk to human properties.