Answer:
0.765m
Explanation:
gravitational potential energy GPE = mass * acceleration due to gravity * height
Given
GPE = 30Joules
Mass m = 4kg
acceleration = 9.8m/s²
Required
Height h
From the formula
h = GPE/mg
h = 30/4(9.8)
h = 30/39.2
h = 0.765m\
Hence the height of the counter is 0.765m
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B. Starting with most recent
image distance,di=10 cm
object distance,do=20cm
magnification, m=di/do
=10/20
=0.5
since the image is virtual, magnification is negative.
therefore m=-0.5
