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8th Science Edited
| Question | Answer |
|---|---|
| Action and reaction forces are not balanced because they_______. | act on different objects. |
| Friction is greater when surfaces are_____. | rougher |
| Newton's first law of motion is also called the law of _____. | inertia |
| If you push a 20-kg box with a force of 10 N, what is its acceleration? | 0.5 m/s (squared) |
| Inertia causes a moving object to ______. | keep moving |
| The SI unit for weight is the ______. | newton |
| Which type of friction do you use when you put on the brakes to stop a bike? | sliding friction |
| Newton's law of universal gravitation states that the force of gravity_________. | affects all objects in the universe is stronger for objects with more mas is stronger for objects that are closer together |
| In the equation F= m x a, if “a” is the acceleration due to gravity, what is “F”? | Weight |
| What is always required to overcome inertia? | unbalanced force |
| Why do ball bearings reduce friction in a wheel? | Rolling friction is less than sliding friction and ball bearings roll instead of slide. |
| Elastic force causes an elastic material to _______. | return to its original shape and push back when pulled. |
| How much an object's motion changes when force is applied to it depends on the strength of the force and the object's ____. | mass |
| On Earth, a mass of 1 kilogram exerts a downward force due to gravity of about _____. | 10 N |
| The only reason that a leaf falls to the ground more slowly than an acorn is that the leaf has _____. | more air resistance |
| Why does engine oil help prevent an engine from overheating? | It reduces friction between moving parts. |
| T or F Momentum is force. | False |
| T or F Both arrows and cannon balls have projectile motion. | True |
| T or F It takes more force to start running than to keep running. | True |
| T or F Rolling friction is weaker than sliding friction. | True |
| T or F Gravity acts only between objects that are close together or touching. | False |
| T or F Weight is measured with a balance. | False |
| T or F Stationary objects generally have at least two forces acting on them | True |
| T or F Static friction is weaker than sliding friction. | False |
| T or F After two objects collide, their combined momentum is always zero. | False |
| T or F The force of gravity acting on an object is measured by weight. | True |
| T or F When you release a stretched bungee cord, it returns to its original shape because of gravity. | False |
| T or F A bowling ball has a greater momentum than a softball if both have the same velocity. | True |
| T or F Any object that is accelerating is changing its speed. | False |
| T or F An object with greater mass has greater inertia. | True |
| T or F Balanced forces are needed to change an object's motion, | False |
| _______ is the ability of a material to return to its original shape after being stretched or compressed. | Elasticity |
| Newton's second law shows that there is a (n) ______ relationship between the acceleration of an object and its mass. | inverse |
| According to Newton's third law of motion, forces always act in _______. | pairs |
| Newton's _______ law of motion relates acceleration to force and mass. | second |
| Any push or pull acting on an object is a (n) _______. | force |
| The law of universal gravitation was proposed by _______. | Isaac Newton |
| The acceleration of any object due to gravity is _____. | 9.8 m/s (squared) |
| ________ is a property of a moving object that makes the object hard to stop. | Momentum |
| According to Newton's ________ law of motion, every action has an equal and opposite reaction. | third |
| ________ showed that gravity is an effect of curves in space and time. | Albert Einstein |
| The force that opposes motion between any two surfaces is ____. | friction |
| Anything that has mass exerts a force of _____ on any other mass. | gravity |
| The SI unit for force is the _____. | newton |
| The combination of all the forces acting on an object is known as the ______ force. | net |
| Friction always produces energy in the form of _____. | heat |
| An elastic material resists changes in ______. | shape |
| Newton's ____ law of motion is also known as the law of inertia. | first |
| You can stand on the floor without slipping because of ____ friction. | static |
| Fluid friction with air is called ______. | air resistance. |
| If the net force acting on any object is zero, the object will ____. | continue to keep doing the same thing. |
| Assume that you drop a rock from the top of a tall cliff and it takes 4 seconds for the rock to fall to the bottom of the cliff. What is the rock's velocity when it reaches the bottom? How do you know? | Second #1 = 9.8 m/s Sec. #2= 19.6 m/s (9.8 x 2) Sec. #3 =29.4 m/s (9.8 x 3 ) Sec. #4 39.2 m/s The original is 9.8 m/s because that is the original velocity due to gravity but as each second passes as it falls it increases 9.8. |
| Compare and contrast balanced and unbalanced forces. | Balanced forces have a net force of zero, the object will continue to do what it is dong. An unbalanced force has a net force greater than zero and will change the velocity of the object. Speeding it up, slowing it down, or changing direction. |
| Explain why it is easier to move a heavy box on a dolly than it is to slide the box over the ground. | The dolly would allow for rolling friction which is weaker than sliding friction therefore the object would be easier to move. |
| Momentum is a property of an object, but it is not always the same for a given object . Explain why. | Momentum is determined by the object's mass and velocity so since it is a given object its mass will not change. The faster that object is going the greater its momentum will be. |
| Explain this statement: Because of inertia, seat belts save lives. | The car forces your body to move forward, when a force acts on the car stopping it, your body continues to move forward. The seat belt is the force that stops your body, without it the windshield or pavement would be what stops your body. |
Created by:
PRO Teacher
Abohn