Newton's First & Second Laws quiz #4 Flashcards
Newton's First & Second Laws quiz #4
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Once a crate is sliding, what keeps it moving? Inertia keeps the crate moving unless acted upon by a net force (such as friction). Which example illustrates Newton's first law? A book remaining at rest on a table until pushed illustrates Newton's first law. What is required in order to determine whether or not an object moves? You must determine if there is a net force acting on the object. How can the motion of an object that is already moving change? The motion can change if an unbalanced force acts on the object. Which statement describes a newton? A newton is the unit of force, equal to 1 kg·m/s². What causes objects to move or stay still? Objects move or stay still depending on whether the net force acting on them is zero or not. What property of matter will keep your body in motion when the car comes to a halt? Inertia keeps your body in motion when the car stops suddenly. What makes stopping quickly in a curve more difficult? Inertia makes stopping quickly in a curve more difficult because the vehicle resists changes in direction and speed. What happens when you decrease the thrust on your scooter? Decreasing thrust reduces the net force, causing the scooter to slow down (decelerate). True or false? If friction didn't exist, what would happen to a moving object? True. If friction didn't exist, a moving object would continue moving at constant velocity. Which of the following best explains Newton's second law? Newton's second law states that the net force on an object equals its mass times its acceleration (F=ma). How do Newton’s laws affect your daily life? Newton's laws explain everyday phenomena such as motion, stopping, and the effects of forces on objects. A metal ball sits motionless on a flat surface. What would make the ball move? An unbalanced force applied to the ball would make it move. How does a wrecking ball have the potential to exert force on another object? A wrecking ball can exert force due to its mass and acceleration when it swings and strikes another object. In what situations do Newton’s laws of motion not apply? Newton's laws do not apply in non-inertial (accelerating) reference frames or at relativistic speeds. Which of Newton’s laws is defined with the equation F=ma? Newton's second law is defined by F=ma. Which method will correctly determine whether the forces on an object are balanced or unbalanced? Calculate the vector sum of all forces; if the net force is zero, forces are balanced; otherwise, they are unbalanced. What will happen to a test dummy during a crash test if its seatbelt is not buckled? The dummy will continue moving forward due to inertia until acted upon by another force. What physics principle results in a spinout? Unbalanced forces and inertia can result in a spinout when a vehicle loses traction. Francisco is holding two magnets close to each other. What will happen when he lets go? The magnets will move according to the net force between them (attraction or repulsion). The force with which a moving object hits another object is called what? It is called impact force. What does ΣF = 0 mean? ΣF = 0 means the sum of all forces (net force) is zero; the object will not accelerate. What does the second part of Newton’s first law say about objects at rest? Objects at rest remain at rest unless acted upon by a net external force. Name three factors that affect the force of impact. Which of these can a driver control? Mass, acceleration, and time of impact affect force; a driver can control speed (acceleration) and time of impact (by braking). A constant net force acts on an object. How does the object's motion change? The object accelerates at a constant rate in the direction of the net force. An object cannot remain at rest unless which condition holds? The net force acting on the object must be zero. Which situation is the best example of inertia? A passenger continuing forward when a car stops suddenly is an example of inertia. How could you tell if a moving object is receiving an unbalanced force? If the object's speed or direction changes, it is receiving an unbalanced force. Who came up with the three laws of motion? Isaac Newton came up with the three laws of motion. What does Newton’s second law of motion say about football? Newton's second law explains that the acceleration of a football depends on the net force applied and its mass. For a stationary box to move, what must be applied? An unbalanced force must be applied to the box. Why does a spaceship with no forces acting on it continue moving even if it has no fuel? Due to inertia, the spaceship continues moving at constant velocity unless acted upon by a net force. A bicycle that travels twice as fast as another when braking to a stop will skid how far compared to the slower one? The faster bicycle will skid a greater distance because it has more momentum to overcome. A 10-N falling object encounters 10 N of air resistance. What is the net force on the object? The net force is zero (10 N downward minus 10 N upward). When a pair of 10-N forces act on a box of candy in opposite directions, what is the net force? The net force is zero. A large rock is motionless on a flat sidewalk. Why? The forces acting on it are balanced; net force is zero. When Marie pushes her desk to the right, which direction does friction act? Friction acts to the left, opposing the direction of motion. What takes longer to stop than a car traveling at the same speed? Heavier vehicles take longer to stop than lighter ones at the same speed. If a monkey floating in outer space throws his hat away, what happens? Both the monkey and the hat move in opposite directions due to conservation of momentum and Newton's third law. If a ball rolls at a constant rate on a flat surface, what is the net force acting on it? The net force is zero if it moves at constant velocity.
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