Presentation on theme: "Chapters 5-6 Test Review Forces & Motion Forces “a push or a pull” A force can start an object in motion or change the motion of an object. A force."— Presentation transcript:
Forces “a push or a pull” A force can start an object in motion or change the motion of an object. A force gives energy to an object
What is a push or a pull? A. canopy B. force C. gruff D. scoff
Representing forces We often use arrows. Larger the arrow, the greater the force Combined balanced forces equal zero Normal force = the force acting perpendicular on an object in contact with another object.
What prevents a book on a table from accelerating downward? A. gravity is pulling on the table B. the table is pushing back with a larger force C. the table is pushing back with an equal force D. air
Balanced Forces Forces opposite in direction and equal in size. Net result: no change in motion.
Unbalanced forces will cause an object to change motion. Unbalanced Forces
When an unbalanced force acts on an object, A. the object’s motion does not change. B. the object accelerates. C. the object will stop. D. the inertia of the object increases.
The net forces acting on any object will cause it to A. keep moving at the same speed. B. accelerate. C. stop. D. swim like a fish.
If a 10 N net forces acts on a 20 kg object it will accelerate at (a=f/m) A. 5 m/s B. 200 m/s C. 0.5 m/s 2 D. 2 m/s 2
What force is needed to accelerate a 4 kg ball at 12 m/s 2 ? (a=f/m) A. 3 m/s B. 48 m/s C. 0.75 N D. 48 N
GRAViTY The pull of one body of mass on another.
What two factors change gravitational force? A. Speed and direction. B. Mass and distance. C. Mass and velocity. D. Speed and momentum.
Weight is a force that depends on gravity and A. mass. B. acceleration. C. friction. D. force.
Acceleration due to gravity All objects fall at the same rate, regardless of their mass or weight The acceleration due to gravity on earth is about 9.8 m/sec 2. This value will change with elevation and location on earth.
Terminal Velocity After a period of free fall, the force of gravity will be canceled by the force of air friction and objects will travel at a constant velocity
The forces acting on a falling leaf are gravity and air resistance. If the leaf falls at a constant rate, A. forces are balanced. B. forces are unbalanced. C. the world will end. D. a leaf never falls at a constant rate.
Newton’s First Law of motion An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an outside force. Often referred to as the Law of Inertia. (the property of matter that resists any change in motion)
The property of matter that resists changes in motion is called A. centripetal motion. B. friction. C. inertia. D. projectile motion.
Inertia is related to A. speed. B. weight. C. mass. D. motion.
An orange might roll off your cafeteria tray when you stop suddenly because of A. the balanced forces acting on the orange. B. the friction forces acting on the orange. C. the centripetal force acting on the orange. D. the orange’s inertia.
Newton’s Second Law of Motion The force of a moving object is directly proportional to the object’s mass and acceleration. The most important of Newton’s laws.
According to Newton’s second law, the acceleration equals the net force divided by the object’s A. mass. B. velocity. C. momentum. D. weight.
Weight and Mass MASS The measure of inertia of an object. The amount of matter in an object Stays constant with changes in location A scalar WEIGHT A measure of the force of gravity acting on an object. Measured in newtons. Changes with changes in location. A vector
Your weight equals your A. mass B. mass divided by the net force acting on it. C. mass times acceleration due to gravity. D. mass times your speed.
Why is your weight less on the moon? A. Mass changes on the moon. B. Gravity is less on the moon. C. Gravity is greater on the moon. D. Weight never changes, only mass changes.
Newton’s Third Law of Motion For every action there is an equal and opposite reaction, or All forces occur in pairs examples:
Newton’s third law of motion describes A. action and reaction forces. B. centripetal forces. C. balanced forces. D. net force.
When one object exerts a force on another, A. the objects will always move as a result of the interaction. B. an equal and opposite force is exerted back on it by the other object. C. the objects will never move due to the forces cancelling each other out. D. one object will always exert a greater force on the other object.
Momentum All moving objects have momentum. How hard is it to stop and object. It is the product of an object’s mass and velocity. the mass matters the speed matters p = mv
What is the momentum of a truck at rest? A. Zero B. Equal to the mass. C. Equal to the weight. D. Trucks do not need to rest.
If a golf ball and marble are rolling at the same speed, which has a greater momentum? A. Golf ball B. Marble C. They have the same. D. I lost my marbles a long time ago!
The product of an object’s mass and velocity is its A. centripetal force. B. net force. C. momentum. D. weight. P = mv