Energy Review

Which combination of units can be used to express work?

• newton · second/meter

• newton · meter/second

• newton/meter

• newton · meter

If a 2.0-kilogram mass is raised 0.050 meter vertically, the work done on the mass is approximately

• 0.10 J

• 0.98 J

• 9.8 J

• 40. J

A total of 640 joules of work is done on a 50.-kilogram object as it is moved 8.0 meters across a level floor by the application of a horizontal force. Determine the magnitude of the horizontal force applied to the object.

• 8.1 N

• 81. N

• 641 N

• 501 N

A student pulls a block along a horizontal surface at constant velocity. The diagram below shows the components of the force exerted on the block by the student. Calculate the work done against friction.

• 18 J

• 24 J

• 30 J

• 48 J

The diagram below shows a 9.8-newton cart being pulled 0.50 meter along a plane inclined at 15° to the horizontal. The amount of work required is 1.3 joules. If the cart was raised 0.50 meter vertically instead of being pulled along the inclined plane, the amount of work done would be:

• 0.0 J

• 1.3 J

• 4.9 J

• 9.8 J

A crane raises a 200-newton weight to a height of 50 meters in 5 seconds. The crane does work at the rate of:

• 8 × 10⁻¹ W

• 2 × 10¹ W

• 2 × 10³ W

• 5 × 10⁴ W

An engine rated at 5.0 × 10⁴ watts exerts a constant force of 2.5 × 10³ newtons on a vehicle. Determine the average speed of the vehicle.

• 2.0 × 10¹ m/s

• 2.0 × 10² m/s

• 2.0 × 10³ m/s

• 2.0 × 10⁴ m/s

A 5.0 × 10²-newton girl develops 250 watts of power as she runs up two flights of stairs to a landing a total of 5.0 meters vertically above her starting point. Calculate the time required for the girl to run up the stairs.

• 5.0 s

• 10.0 s

• 15.0 s

• 20.0 s

Which term identifies a scalar quantity?

• force

• energy

• displacement

• velocity

Energy is measured in the same units as

• force

• momentum

• power

• work