Review Midterm Unit 3 – Forces and Energy

What is the equation for density?

• density = mass + volume

• density = mass - volume

Look at the list of substances.

water ice wood air iron

which substance is the lowest density?

• water

• ice

• wood

• air

• iron

If water has a density of 1.0 g/cm3.

A substance called LDPE has a density of 0.91 g/cm3.

Explain whether LDPE will float or sink in water.

• It will sink, because its density is lower than water.

• It will float, because its density is lower than water.

• It will sink, because its density is same as water.

What is the unit of temperature?

• °C

• J

• N

• Kg

A hairdryer uses 1500 J of electrical energy in 1 second.

The hairdryer changes 1300 J of this to useful thermal energy in 1 second.

Calculate the quantity of energy that is wasted by the hairdryer in 1 second.

• 300 J

• 200 J

• 1300 J

• 2800 J

Two objects, A and B, are placed in contact with each other.

Thermal energy initially flows from A to B.

Explain the conclusion that can be made about the initial temperatures of A and B.

• A is hotter than B

• A is colder than B

• A and B has same temperature.

An object has a mass of 60 g and a volume of 50 cm3.

Calculate the density of this object and give the unit with your answer.

• 1.2 g/cm³

• 0.8 g/cm³

• 3000 g/cm³

• 110 g/cm³

The density of water is 1.0 g/cm³. If an object has a density of 1.6 g/cm³.

Will it float or sink in water?

• Sink

• Float

Two beakers, X and Y, contain water at the same temperature.

Beaker X contains 50 cm³ of water.

Beaker Y contains 100 cm³ of water.

Explain how the average energy of the particles in beakers X and Y compare.

• X has more average kinetic energy than Y

• X has less average kinetic energy than Y

• X has same average kinetic energy as Y

Two beakers, X and Y, contain water at the same temperature.

Beaker X contains 50 cm³ of water.

Beaker Y contains 100 cm³ of water.

Explain how the heat of the particles in beakers X and Y compare.

• X has more total energy than Y

• X has less total energy than Y

• X has same total energy as Y