PHY 102 Exam 1

You would have the largest mass of gold if it weighed 1 N on the Correct answer- Moon A kilogram is a measure of an object's Correct answer- Mass Where is your weight greater: on Earth or on the Moon? How about your mass? Correct answer- Your weight is greater on Earth than on the Moon. Your mass is the same in both locations, or in any location. An object that has twice as much mass as another object also has twice as much Correct answer- inertia measure of how much inertia an object has Correct answer- mass While a crate rests on a horizontal floor the friction force acting on the crate is Correct answer- between zero and the weight of the crate. A stone is dropped off a cliff and is in free fall. Every second that the stone is falling, its acceleration Correct answer- is constant but its velocity is increasing How would air resistance affect the travel time? Correct answer- Air resistance would increase travel time The speed of a vertically-thrown ball at the top of its path is Correct answer- zero Science greatly advanced when Galileo favored Correct answer- experiment What is the acceleration of an object in free fall at Earth's surface? Correct answer- 9.8 m⋅s^2 You're driving in a car at 50 km/h and bump into a car ahead traveling at 48 km/h in the same direction. The speed of impact is Correct answer- 2 km/h A bucket of cement is raised by a rope at constant speed at a construction site. The upward force on the bucket supplied by the rope is Correct answer- equal to the force of gravity. While in an airplane flying at 100 km/h you look down from the window and spot another airplane flying at the same speed in the opposite direction. Relative to you, the speed of the spotted plane is Correct answer- 200 km/h. What did Galileo incorporate in his study of motion that Aristotle overlooked? Correct answer- the role of time The gain in speed each second for a freely falling object is about Correct answer- 10 m/s When a falling object gains 10 m/s each second, its acceleration is Correct answer- 10 m/s^2 An object is at rest. The forces acting on the object _______. Correct answer- are equal in magnitude have a vector sum of zero are opposite in direction acceleration Correct answer- speed/time Nellie runs the length of a 100-yard football field in a time of 20 seconds. Her average running speed is Correct answer- 5 yards/s. The acceleration of a cart moving down an inclined plane (a ramp) Correct answer- Constant The equilibrium rule F = 0 applies to Correct answer- objects or systems at rest. objects or systems in uniform motion in a straight line. When you stand at rest on a floor, the number of vertical forces acting on you is Correct answer- two On the surface of the Moon where acceleration due to gravity is less, a person's hang time would be Correct answer- longer Your weight is Correct answer- the gravitational attraction between you and Earth. The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about Correct answer- 1.2 m Compared with a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much Correct answer- inertia. volume. mass. When a skydiver of mass 100 kg experiences air resistance of 400 N, her acceleration is Correct answer- 0.6g first law Correct answer- inertia second law Correct answer- acceleration third law Correct answer- action-reaction The air resistance of falling is greatly affected by an object's frontal area and Correct answer- speed A ball tossed vertically upward reaches its highest point and then falls back to its starting point. During this up-and-down motion the acceleration of the ball is always Correct answer- directed downward A 10-N block and a 1-N block lie on a horizontal frictionless table. To push them with equal acceleration, we would have to push with Correct answer- 10 times as much force on the heavier block. When you toss a coin straight up, it moves upward, turns around, and drops. During this time the acceleration of the coin is Correct answer- downward and constant. When an object falls through the air, as velocity increases its acceleration Correct answer- decreases A force of 1 N accelerates a 1-kg mass at 1 m/s2. The acceleration of a 2-kg mass acted upon by a force of 2 N is Correct answer- the same The reason a 20-kg rock falls no faster than a 10-kg rock in free fall is that _______. Correct answer- the ratio of weight to mass is the same A commercial jet has a mass of 5,000 kg and the thrust of its engine is 10,000 N. The acceleration of the jet when taking off is Correct answer- 2 m/s^2 A commercial jet has a mass of 5,000 kg and the thrust of its engine is 10,000 N. The acceleration of the jet when taking off is Correct answer- 2400 N A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10- kg brick is Correct answer- 10 times as much as the force on the 1-kg book. If you drop an object, it will accelerate downward at a rate of 10 m/s2. If you instead throw it downward, its acceleration (in the absence of air resistance) will be Correct answer- 10 m/s^2 A roller coaster car at an amusement park carrying 1 passenger takes 3 min to make its ride from start to finish. Neglecting friction, a car with 5 passengers would take Correct answer- the same time Two people, one twice as massive as the other, attempt a tug-of-war with 12 m of rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of Correct answer- 4 m The acceleration of a rocket increases as it travels upward from the ground mainly because Correct answer- the mass of the rocket decreases as fuel is burned. A space probe in remote outer space continues moving Correct answer- even though no force acts on it When you step off a bus moving at 10 m/s, your horizontal speed when you meet the ground is Correct answer- 10 m/s A ball thrown straight up takes 10 s to go up and return to the ground. Because of air resistance, the time taken for the ball just to go up is Correct answer- less than 5s A heavy rock and a light rock in free fall have the same acceleration. Both rocks have the same acceleration because Correct answer- ratio of force to mass is the same What is the net force on an apple that weighs 1 N when you hold it at rest above your head? What is the net force on the apple when you release it? Correct answer- 0N 1N A car has a certain maximum acceleration. When it tows another twice-as-massive car its maximum acceleration is Correct answer- one-third A ball is thrown vertically upward. Because of air resistance, its speed when returning to its starting level compared with its initial speed is Correct answer- less You toss a ball upward where air resistance is negligible. After the ball leaves your hand the force on it Correct answer- is the single force due to gravity, always directed downward. Exert 1 N for a distance of 1 m in 1 s and you deliver a power of Correct answer- 1 W A car traveling along the highway needs a certain amount of braking force to stop. More braking force is required when the car Correct answer- has more momentum but must stop in the same distance. has more mass but has the same speed and must stop in the same distance. has the same momentum but must stop in a shorter distance. From the same height you simultaneously drop a lightweight tennis ball and a heavyweight bowling ball. When they hit the floor they have the same Correct answer- speed Two identical gliders slide toward each other on an air track. One glider moves at 1 m/s and the other glider moves at 2 m/s. They collide and stick. The combined gliders move at Correct answer- 1/2 m/s A golf ball is thrown at and bounces backward from a massive bowling ball that is initially at rest. After the collision, compared to the golf ball, the bowling ball has more Correct answer- momentum, but less kinetic energy. The ultimate source of energy from fossil fuels is the Correct answer- sun The impulse-momentum relationship is a direct result of Correct answer- Newton's Second Law A cannonball fired from a long-barrel cannon will have a greater muzzle velocity because the cannonball receives a greater Correct answer- impulse If your friend pushes a stroller four times as far as you do while exerting only half the force, which one of you does more work? How much more? Correct answer- your friend does twice as much work If a power plant is 30% efficient, and the transmission system that delivers power to consumers is 60% efficient, then the overall efficiency is Correct answer- 18 % The conservation of momentum is closely related to Correct answer- Newton's Third Law A 2500-N pile driver ram falls 10 m and drives a post 0.1 m into the ground. The average force on the post is Correct answer- 250,000 A rifle of mass 2 kg is horizontally suspended by a pair of strings so that recoil can be measured. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about Correct answer- 1 m/s When a 100-kg astronaut ejects 0.1 kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is Correct answer- 0.05 m/s In raising a 5000-N piano with a pulley system, for every 1 m of rope pulled down, the piano rises 0.1 m. Ideally, this means the force needed to lift the piano is Correct answer- 500 N The distinction between impulse and force involves the Correct answer- time the force acts. Railroad car A rolls at a certain speed and collides with car B of the same mass. If this railroad cars couple together after colliding inelastically, how does their speed after the collision compare with the initial speed of car A? Correct answer- Speed after coupling is half as much as initially. A clerk can lift containers a vertical distance of 1 m, or roll them up a 2-m-long ramp to the same elevation. With the ramp, the applied force needed is Correct answer- half as much Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two-ball system? Correct answer- 0 kg•m/s The most energy per unit mass can be extracted from Correct answer- uranium. A 30-kg girl and a 25-kg boy face each other on friction-free roller blades. The girl pushes the boy, who moves away at a speed of 1.0 m/s. The girl's speed is Correct answer- 0.83 m/s.