Define (i) work, (ii) power, and give the unit of measurement for each one - Leaving Cert Physics - Question 6 - 2007

The work done by the lift's motor can be calculated using the formula:

$W = F imes d$

Where:

• $W$ = Work (J)
• $F$ = Force or total weight (N) = 8000 N
• $d$ = distance moved (m) = 25 m

Substituting the values:

$W = 8000 imes 25 = 200000 J$

Power can be calculated using the formula:

$P = \frac{W}{t}$

Where:

• $P$ = Power (W)
• $W$ = Work done (J) = 200000 J
• $t$ = time (s) = 40 s

Substituting the values:

$P = \frac{200000}{40} = 5000 W = 5 kW$

The energy gained by the person in taking the lift is equal to the work done against gravity:

Energy gained = Work done = 200000 J.

First, convert 2 minutes to seconds:

$2 ext{ minutes} = 120 ext{ seconds}.$

Using the power formula:

$P = \frac{W}{t}$

Where:

• Work done = 200000 J
• Time = 120 s

Substituting the values:

$P = \frac{200000}{120} \approx 1666.67 W.$

1. Reduces physical exercise: Using lifts can lead to a sedentary lifestyle since people may opt for lifts instead of using stairs, resulting in less physical activity.
2. Mechanical failure risk: Lifts may malfunction, potentially leading to entrapment or hazards during an emergency.