Unit 2 Review

Energy is the ability to do work. In which of these examples does using energy cause work to be done?

• A girl kicks a ball across a field

• A boy holds a suitcase by his side

• A pitcher holds a ball in his glove

• A woman reads instructions for assembling her bicycle

How is the energy in the food we eat an example of chemical potential energy?

• It isn't; food stores kinetic energy

• It isn't; chemical potential energy is only found in fossil fuels

• Food is broken down and then moves through the digestive system

• The chemical bonds in the food store energy that is released when we eat it

Answer explanation

D is correct because foo contains chemical potential energy that is released once consumed

A child has a mass of 35 kg. The child is running across a field and has a speed of 3 m/s2. What is the kinetic energy of the child?

• 315 J

• 157.5 J

• 52.5 J

• There is not enough information to determine the KE

What is the difference between input force and output force?

• Input Force is the force a machine exerts on an object, and output force is the force exerted on a machine.

• Input force is the force exerted on a machine, and output force is the force a machine exerts on an object.

• Input force is a measure of the machine's efficiency, and output force is a measure of the mechanical advantage of the machine.

• Input force is a measure of the mechanical advantage of the machine, and output force is a measure of the machine's efficiency.

As you pull down on a pulley, the load attached to the pulley is lifted. How has the pulley changed the way work is done?

• It made the load lighter

• It made the load heavier

• It lifted the load more quickly

• It changed the direction of force

The motion of a fish swimming in a fish tank is an example of which type of energy?

• Kinetic

• Chemical

• Potential

• Gravitational

A worker moves a heavy load into a house with the aid of an inclined plane. If the plane has a length of 6.2 meters and a height of 1.7 meters, what is its ideal mechanical advantage?

• 3.65

• 7.9

• 10.54

• 0.27

Name three simple machines and a real world example for each.

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