Work, Power, and Energy Quiz

A 10 N force moves an object 5 m in the direction of the force. How much work is done?

• 50 J

• 5 J

• 15 J

• 500 J

Answer explanation

Work is calculated using the formula: Work = Force × Distance. Here, Work = 10 N × 5 m = 50 J. Therefore, the correct answer is 50 J.

Work is defined as:

• Force divided by distance

• Force applied over a distance in the direction of force

• Energy stored in an object

• Power per unit time

Answer explanation

Work is defined as the product of force and the distance over which it is applied in the direction of the force. Thus, the correct choice is 'Force applied over a distance in the direction of force'.

A force is applied perpendicular to an object’s displacement. How much work is done?

• Zero

• Maximum work

• Depends on speed

• Infinite

Answer explanation

When a force is applied perpendicular to the displacement, the angle between the force and displacement is 90 degrees. The work done is calculated as W = F * d * cos(θ). Since cos(90° = 0), the work done is zero.

If an object moves at a constant velocity, how much net work is done?

• Zero

• Maximum

• Depends on friction

• Cannot be determined

Answer explanation

When an object moves at a constant velocity, the net force acting on it is zero, which means no net work is done. Therefore, the correct answer is zero.

A force of 20 N moves an object 10 m at an angle of 60°. What is the work done?

• 100 J

• 200 J

• 50 J

• 20 J

Answer explanation

Work is calculated using the formula: Work = Force × Distance × cos(θ). Here, Work = 20 N × 10 m × cos(60°) = 20 N × 10 m × 0.5 = 100 J. Thus, the correct answer is 100 J.

Power is defined as:

• Work done per unit time

• Force applied per unit time

• Energy per unit distance

• Momentum per unit mass

Answer explanation

Power is defined as the rate at which work is done, which is expressed as work done per unit time. This makes the first choice, 'Work done per unit time', the correct definition of power.

The SI unit of power is:

• Newton

• Joule

• Watt

• Pascal

Answer explanation

The SI unit of power is the Watt, which measures the rate of energy transfer. Newton measures force, Joule measures energy, and Pascal measures pressure, making Watt the correct choice for power.

A machine does 600 J of work in 3 seconds. What is its power?

• 200 W

• 1800 W

• 2 W

• 60 W

Answer explanation

Power is calculated as work done divided by time. Here, power = 600 J / 3 s = 200 W. Therefore, the correct answer is 200 W.

What happens to power if the work remains the same but is done in less time?

• Power increases

• Power decreases

• Work remains constant

• Time has no effect on power

Answer explanation

Power is defined as work done per unit time. If the work remains constant but is done in less time, the power must increase, as power is inversely related to time. Therefore, the correct answer is that power increases.

Which of the following represents 1 Watt?

• 1 Joule per second

• 1 Joule per meter

• 1 Newton per second

• 1 Newton-meter per second

Answer explanation

1 Watt is defined as 1 Joule of energy transferred per second. Therefore, the correct representation of 1 Watt is '1 Joule per second', making it the right choice among the options.