10.4 Energy & efficiency

No machine in existence has 100% efficiency due to ____________________.

• magic
• friction
• smoke
• input

Tags

NGSS.MS-PS3-5

What is the efficiency of a machine if 55.3 J of work are done on the machine, but only 14.3 J or work are done by the machine?

• 0.25 Joules
• 26%
• 3.86 Joules
• 386%

Total energy = 200J
Useful energy = 20J

Workout the efficiency of this lightbulb.
 $efficiency\ =\ \frac{useful\ enegy}{total\ energy\ in}\ \times100$  

• 100%

• 80%

• 40%

• 10%

Total energy = 350J
Useful energy = 70J

Workout the efficiency of this iphoneX.
 $efficiency\ =\ \frac{useful\ energy}{total\ energy\ in}\ \times100\%$  

• 100%

• 80%

• 40%

• 20%

Total energy = 34000J
Useful energy = 340J

Workout the efficiency of this vintage VW Beetle.
 $efficiency\ =\ \frac{useful\ energy}{total\ energy\ in}\ \times100\%$  

• 100%

• 10%

• 40%

• 20%

This car needs 8600J of energy to power it. If 5000J is changed into useful energy, how much energy is wasted?

• 13600J

• 3600J

• 5000J

• 8600J

A car transfers 100 J of chemical energy in order to gain 50 J of kinetic energy. The efficiency of the car is

• 20%

• 0.5%

• 50%

• 200%

What is the efficiency of a machine if 55.3 J of work are done on the machine, but only 14.3 J is produced by the 1machine?

• 0.25 J
• 26%
• 386%
• 3.86 J

Tags

NGSS.HS-PS3-3

What is the efficiency of the machine if the input is 263 J and the output is 142 J? 

• 6.26%
• 54%
• 100%
• 260%

What is the efficiency of a machine that has work input of 40 joules and work output of 35 joules?

• 87.50%
• 1200
• 1.142
• 114%