Question

Determine the mechanical energy of this object a 1kg pendulum at a height of 1-meter

A. 9.8J
B.7.8J
C.11.8J
D.2j

Answer 1

A

Explanation:

Mechanical energy (ME) is Kinetic energy + potential energy

Where

Kinetic Energy (KE) = 1/2 * m * v^2

where m is the mass (in kg) and v is the speed of the object (in m/s)

and

Potential Energy (PE) = m*g*h

Where m is the mass (in kg) and g is the gravitational constant (9.81 m/s) and h is the height (in meters)

Hence

ME = KE + PE (note the pendulum DOES NOT have any speed, so v = 0, and thus KE = 0)

So,

`ME=KE+PE\\ME=(1)/(2)mv^2+mgh\\ME=(1)/(2)(1)(0)^(2)+(1)(9.81)(1)\\ME=0+9.81\\ME=9.81`

Hence, Mechanical Energy is 9.8 Joules (rounded to 1 decimal place). Correct answer is A.