Work, Energy & Power
Q. If a machine does 500 J of work in 10 seconds, what is its power?
A.
50 W
B.
100 W
C.
200 W
D.
500 W
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Solution
Power = Work / Time = 500 J / 10 s = 50 W.
Correct Answer: A — 50 W
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Q. If a machine does 500 Joules of work in 10 seconds, what is its power output?
A.
50 Watts
B.
100 Watts
C.
200 Watts
D.
500 Watts
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Solution
Power is calculated as work done divided by time taken. Here, Power = 500 J / 10 s = 50 W.
Correct Answer: B — 100 Watts
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Q. If a machine has an efficiency of 80% and it consumes 1000 J of energy, what is the useful work output?
A.
800 J
B.
1000 J
C.
200 J
D.
600 J
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Solution
Useful work output can be calculated using the formula: Useful Work = Efficiency * Input Energy. Here, Useful Work = 0.8 * 1000 J = 800 J.
Correct Answer: A — 800 J
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Q. If a person lifts a 10 kg object to a height of 5 m in 2 seconds, what is the power exerted?
A.
25 W
B.
50 W
C.
75 W
D.
100 W
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Solution
First, calculate the work done: W = mgh = 10 kg * 9.8 m/s² * 5 m = 490 J. Then, P = W/t = 490 J / 2 s = 245 W.
Correct Answer: B — 50 W
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Q. If a person lifts a 10 kg object to a height of 5 m in 5 seconds, what is the power exerted?
A.
100 W
B.
200 W
C.
300 W
D.
400 W
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Solution
First, calculate the work done: W = mgh = 10 kg * 9.8 m/s² * 5 m = 490 J. Then, power is P = W/t = 490 J / 5 s = 98 W.
Correct Answer: B — 200 W
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Q. If a person lifts a 10 kg weight to a height of 2 meters in 4 seconds, what is the power exerted?
A.
50 W
B.
100 W
C.
200 W
D.
250 W
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Solution
First, calculate the work done: W = mgh = 10 kg * 9.8 m/s² * 2 m = 196 J. Then, power is P = W/t = 196 J / 4 s = 49 W, approximately 50 W.
Correct Answer: B — 100 W
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Q. If a person lifts a 50 kg box to a height of 2 meters in 5 seconds, what is the power exerted?
A.
200 W
B.
400 W
C.
500 W
D.
600 W
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Solution
The work done against gravity is W = mgh = (50 kg)(9.8 m/s²)(2 m) = 980 J. Power is P = W/t = 980 J / 5 s = 196 W, approximately 200 W.
Correct Answer: B — 400 W
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Q. If a person lifts a 50 kg object to a height of 2 meters in 5 seconds, what is the power exerted?
A.
200 W
B.
400 W
C.
500 W
D.
600 W
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Solution
The work done is W = mgh = 50 kg * 9.8 m/s^2 * 2 m = 980 J. Power is W/t = 980 J / 5 s = 196 W, approximately 200 W.
Correct Answer: B — 400 W
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Q. If a person lifts a weight of 100 N to a height of 2 m in 4 seconds, what is the power exerted?
A.
50 Watts
B.
100 Watts
C.
200 Watts
D.
25 Watts
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Solution
Work done = Force × Distance = 100 N × 2 m = 200 J. Power = Work / Time = 200 J / 4 s = 50 W.
Correct Answer: A — 50 Watts
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Q. If a^3 = 27, then the value of a is?
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Solution
Taking the cube root of both sides, a = 27^(1/3) = 3.
Correct Answer: C — 3
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Q. If a^3 = 27, what is the value of a?
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Solution
Since 27 = 3^3, we have a = 3.
Correct Answer: C — 3
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Q. If a^x = b^y and a = b^k, what is the relationship between x, y, and k?
A.
x = ky
B.
y = kx
C.
x + y = k
D.
x - y = k
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Solution
Substituting a = b^k into a^x = b^y gives (b^k)^x = b^y, leading to kx = y, hence x = ky.
Correct Answer: A — x = ky
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Q. If a^x = b^y, then log_a(b) is equal to?
A.
y/x
B.
x/y
C.
x+y
D.
y-x
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Solution
From a^x = b^y, taking log_a on both sides gives log_a(b^y) = x, hence y * log_a(b) = x, thus log_a(b) = y/x.
Correct Answer: A — y/x
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Q. If log_10(1000) = x, what is the value of x?
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Solution
Since 1000 = 10^3, log_10(1000) = 3, thus x = 3.
Correct Answer: B — 3
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Q. If x^3 - 8 = 0, what is the value of x?
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Solution
x^3 = 8 => x = 2
Correct Answer: A — 2
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Q. If x^3 = 8, then the value of x is?
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Solution
Taking the cube root of both sides, x = 8^(1/3) = 2.
Correct Answer: A — 2
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Q. If x^4 = 81, what is the value of x?
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Solution
Taking the fourth root, x = 81^(1/4) = 3.
Correct Answer: A — 3
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Q. In a hydraulic lift, if the input power is 2000 W and the output power is 1800 W, what is the efficiency of the lift?
A.
90%
B.
80%
C.
70%
D.
75%
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Solution
Efficiency is calculated as (Output Power / Input Power) * 100%. Here, efficiency = (1800 W / 2000 W) * 100% = 90%.
Correct Answer: B — 80%
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Q. In a hydraulic lift, if the input power is 500 W and the efficiency is 80%, what is the output power?
A.
400 W
B.
500 W
C.
600 W
D.
700 W
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Solution
Output power can be calculated using the formula: Output Power = Efficiency * Input Power. Here, Output Power = 0.8 * 500 W = 400 W.
Correct Answer: A — 400 W
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Q. In an electric circuit, if the voltage is 12 V and the current is 3 A, what is the power?
A.
36 W
B.
9 W
C.
4 W
D.
12 W
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Solution
Power in an electric circuit is given by P = V * I. Here, P = 12 V * 3 A = 36 W.
Correct Answer: A — 36 W
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Q. In an electric circuit, if the voltage is doubled while the resistance remains constant, what happens to the power?
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
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Solution
Power in an electric circuit is given by P = V^2/R. If V is doubled, P becomes (2V)^2/R = 4V^2/R, which is quadrupled.
Correct Answer: C — It quadruples
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Q. The expression 4^(x+1) can be rewritten as?
A.
2^(2x+2)
B.
2^(x+1)
C.
2^(x+2)
D.
4^x
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Solution
4^(x+1) = (2^2)^(x+1) = 2^(2(x+1)) = 2^(2x+2).
Correct Answer: A — 2^(2x+2)
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Q. The value of (x^2)^3 is equal to?
A.
x^5
B.
x^6
C.
x^7
D.
x^8
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Solution
Using the power of a power property, (a^m)^n = a^(m*n), we get (x^2)^3 = x^(2*3) = x^6.
Correct Answer: B — x^6
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Q. What is the relationship between power, force, and velocity?
A.
P = F * v
B.
P = F / v
C.
P = F + v
D.
P = F - v
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Solution
Power is defined as the product of force and velocity in the direction of the force, given by P = F * v.
Correct Answer: A — P = F * v
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Q. What is the relationship between power, voltage, and current in an electrical circuit?
A.
P = V/I
B.
P = VI
C.
P = V + I
D.
P = V - I
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Solution
In an electrical circuit, power is given by the formula P = VI, where P is power, V is voltage, and I is current.
Correct Answer: B — P = VI
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Q. What is the SI unit of power?
A.
Joule
B.
Watt
C.
Newton
D.
Pascal
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Solution
Power is defined as the rate at which work is done or energy is transferred. The SI unit of power is the Watt (W), which is equivalent to one Joule per second.
Correct Answer: B — Watt
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Q. What is the value of (2^3) * (2^2)?
A.
2^5
B.
2^6
C.
2^7
D.
2^8
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Solution
Using the property of exponents, (2^3) * (2^2) = 2^(3+2) = 2^5.
Correct Answer: A — 2^5
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Q. What is the value of (4^2) * (4^3)?
A.
64
B.
128
C.
256
D.
1024
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Solution
4^2 * 4^3 = 4^(2+3) = 4^5 = 1024
Correct Answer: C — 256
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Q. What is the value of (x^2)^3?
A.
x^5
B.
x^6
C.
x^7
D.
x^8
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Solution
Using the power of a power property, (x^2)^3 = x^(2*3) = x^6.
Correct Answer: B — x^6
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Q. What is the value of 2^(3x) * 2^(2x)?
A.
2^(5x)
B.
2^(6x)
C.
2^(x)
D.
2^(x+5)
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Solution
Using the property of exponents, 2^(3x) * 2^(2x) = 2^(3x + 2x) = 2^(5x).
Correct Answer: A — 2^(5x)
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