Unbalanced Forces & Motion

Balanced ForcesAre forces that have a net force of zeroEqual forces in opposite directionsBalanced forces DO NOT change the

motion of objects

Unbalanced ForcesHas a net force that is not zeroUnbalanced forces DO change the motion

of objects

Object Moves to the Left

What are forces that have a net force of zero called?a. Balancedb. Unbalancedc. Equald. accelerating

What type of force allows you to stand up from a chair?a. Balancedb. Unbalancedc. Equald. Opposite

A ball has two forces acting on it. One force is pushing it to the left, and a larger force is pushing it to the right. In which direction will the ball move?

A. RightB. LeftC. UpD. Down

Energy and Machines

EnergyIs the capacity to do workEnergy can be used to move muscles,

operate machines, cook meals, and heat rooms.

When you stand up, your body uses energy to hold itself up. Energy is needed to act against the force of gravity.

MachinesMachines also use energy to act against

gravity and friction.

A machine is something that replaces human effort.

Whenever a machine moves against the pull of gravity it uses energy.

Forms of EnergyHeat energy, light energy, sound energy,

electrical energy, chemical energy, and mechanical energy

One form of energy can change into another form of energy.

A light bulb changes electrical energy to light energy and heat energy.

Did you know?Some scientist have built machines that harness the energy from tides and waves. These machines turn the movement of water waves and tides into power that can be used to light nearby homes and businesses.

What is a device that replaces human effort?A. A chemicalB. A machineC. A heaterD. gravity

What is needed to operate a machine?a. Forceb. Energyc. Liftd. Motion

Why does a machine that lifts boxes off the ground need energy?a. It needs energy to pull against the force

of gravity.b. It needs energy to pull against an

electrical force.c. It needs energy to pull against a chemical

force.d. It needs energy to pull against a heat

source.

Which kind of energy is shown in this illustration of a water wheel?a. Chemical energy b. Heat energyc. Light energyd. Mechanical energy