Rosie (mass 41 kg) pushes a box with a horizontal

force of 140 N (31.472 lb) at a speed
25 m/min.
A. What is Rosie’s power output?
Answer in units of W.

B.What energy is produced by a 300 W lightbulb
lit for 4.1 hours?
Answer in units of J

P = W/t or in this case P = Fv

change the m/min into m/sec

b) Just rearrange E = Pt. Again change units into seconds, not hours

To find Rosie's power output, we can use the formula:

Power = Force × Velocity

A. The force Rosie exerts on the box is 140 N, and the velocity at which she pushes the box is 25 m/min. However, we need to convert the velocity to m/s since the SI unit for power is watts (W) which is equivalent to joules per second (J/s).

To convert 25 m/min to m/s, we divide by 60 since there are 60 seconds in a minute:

Velocity = 25 m/min ÷ 60 s/min = 0.4167 m/s

Now, we can calculate the power output using the given force and velocity:

Power = 140 N × 0.4167 m/s ≈ 58.333 W

Therefore, Rosie's power output is approximately 58.333 W.

B. To find the energy produced by a lightbulb, we can use the formula:

Energy = Power × Time

The power of the lightbulb is given as 300 W, and the time it is lit for is 4.1 hours. However, we need to convert the time to seconds since the SI unit for energy is joules (J).

To convert 4.1 hours to seconds, we multiply by 60 to get minutes and then multiply by 60 again to get seconds:

Time = 4.1 hours × 60 min/hour × 60 s/min = 14,760 s

Now, we can calculate the energy using the given power and time:

Energy = 300 W × 14,760 s = 4,428,000 J

Therefore, the energy produced by the 300 W lightbulb when lit for 4.1 hours is approximately 4,428,000 J.