Question

An engine develops 10 kW of power. How much time will it take to lift the mass of 200 kg to a height of 40 m. (Take g = 10 m s⁻¹ ) *

(a) 4 s

(b) 6 s

(c) 8 s

(d) 10 s


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Answer 1

Answer:

power is Power=(m∗g∗h)/t

t=m∗g∗h/power=(200∗40∗10)/10∗10

3

=8s

Explanation:

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Answer 2

Given

Power = 10 kW

Mass = 200 kg

Height = 40 m

g = 10 m/s²

To Find

Time

Solution

We know that

$\sf \longrightarrow P=\dfrac{mgh}{t}$

Here

• P = Power
• m = Mass
• g = Acceleration due to gravity
• t = Time

Units

• P = Watt
• m = kg
• g = m/s²
• t = sec

According to the question

We are asked to find time

Therefore

$\sf \longrightarrow t=\dfrac{mgh}{P}$

Given that

Power = 10 kW

Mass = 200 kg

Height = 40 m

g = 10 m/s²

Hence

• P = 10 kW = 10000 W
• m = 200 kg
• h = 40 m
• g = 10 m/s²

Substituting the values

We get

$\sf \longrightarrow t=\dfrac{200 \times 10 \times 40}{10000} \ sec$

$\sf \longrightarrow t=\dfrac{80000}{10000} \ sec$

Therefore

$\sf \longrightarrow t=8 \ sec$

Hence

Time = 8 seconds