Question

A rock on the edge of a cliff has a 1500 J of potential energy. The rock falls 20 m to

the ground. What is the mass of the rock? What force will be exerted on the ground on
impact?

Answer 1

Answer: Mass of the rock= 7.65g

Force exerted on the ground = 74.9N

Step-by-step explanation:

potential energy = mass × gravity ×height

1500J = y × 9.8 × 20

1500J=196y

1500 ÷ 196 = y

y= 7.65g

force= mass × gravity

= 7.65 ×9.8

=74.9N

Answer 2

Mass = 7.65kg

Force = 75N

Step-by-step explanation:

Energy Potential = mass • gravity • height

1500 J = mass • 9.8 • 20

1500 J/(9.8 m/s/s •20 m) = mass

7.65 kg = mass

Force = mass • acceleration

Force = 7.65 • 9.8m/s/s

Force = 75 N

We could also do 1500J/20m as gravity is divided in one and then multiplied again

Force = (1500J • 9.8m/s/s)/(9.8m/s/s • 20m)

Force = 1500J/20m

Force = 75N

this makes sense as Energy is defined as Newton metres as seen by the work formula, Work = Force • distance