Question

a) if a 75w light bulb is left on for 2.0 hrs how much work is done?

b)a winch thats powered by a 156W motor lifts crate 9.8m in 11 seconds. what is the mass of the create?

Answer 1

a) work is form of energy as,

W = P*t

where W is work done, P is power and t is time.

W = 75 * 2* 60 *60

W = 5.4 * 10^5 J

b) as power is the work done per unit of time,

P = W/t

work is a type of energy and the object at a certain height have potential energy.

P = m*g*h/t

where m is the mass of crate, g is accelaration due to gravity and h is the height

using the known values,

156 = m*9.8*9.8/11

solving for m,

m = 17.86 kg