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### 29 Cards in this Set

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 What makes an object speed up, slow down, or change directions? when a net force is applied Seat belts and car seats provide protection. When a car comes to a stop, your seat belt and the friction between you and the seat provide the unbalanced backward force that is needed to bring you to a stop as the car stops. What determines how much an object speeds up or slows down? the unbalanced force on an object net force equation net force= mass x acceleration (F=ma) m= kg a= m/s2 F= kgm/s2 Force is measured in newtons (N) 1 N = 1 kg × 1 m/s2 = 1 kgm/s2 For equal forces, a larger mass accelerates __ less For equal masses, a greater force produces a ___ acceleration greater acceleration depends on force and mass The acceleration of an object is proportional to the net force on the object and inversely proportional to the object’s mass. How are weight and mass related? Weight is equal to mass times free-fall acceleration. weight equation weight = mass x free-fall acceleration, or w = mg Weight is different from mass. – mass = a measure of the amount of matter in an object – weight = the gravitational force an object experiences because of its mass Why do objects fall to the ground when dropped? All objects in the universe attract each other through the force of gravity. Newton’s law of universal gravitation gives the size of the gravitational force between two objects (equation) F= G (m1m2) / d2 All matter is affected by gravity (2) 1. size of the masses 2. distance between masses gravitational force ___ as mass increases increases gravitational force ___ as distance increases decreases What is the relationship between free-fall acceleration and mass? In the absence of air resistance, all objects falling near Earth’s surface accelerate at the same rate regardless of their mass. how can air resistance balance weight? by terminal velocity Why does a projectile follow a curved path? Projectile motion has two components—horizontal and vertical. When the two motions are combined, they form a curved path. Projectile motion has a horizontal component. After you have thrown a ball, no horizontal forces are acting on the ball (if air resistance is ignored). So, the horizontal component of velocity of the ball is constant after the ball leaves your hand. Projectile motion also has a vertical component. When you throw a ball, gravity pulls it downward, which gives the ball vertical motion. In the absence of air resistance, gravity on Earth pulls objects that are in projectile motion downward with an acceleration of 9.8 m/s2, just as it pulls down all falling objects. What happens when an object exerts a force on another object? When one object exerts a force on a second object, the second object exerts a force equal in size and opposite in direction on the first object. Forces always occur in pairs. For every action force, there is an equal and opposite reaction force. What do forces in a pair do not do? act on the same object. How do you calculate the momentum of an object? For movement along a straight line, momentum is calculated by multiplying an object’s mass and velocity. Momentum equation momentum = mass x velocity, or p = mv When does momentum increase? when mass and velocity increase When there is more time, what happens to force? force decreases What is the total momentum after objects collide? The total momentum of two or more objects after a collision is the same as it was before the collision. In other words, the total amount of momentum in an isolated system is conserved.