Physics unit 2: Forces
A 6-N falling object encounters 6 N of air resistance. The magnitude of the net force on the object is
0 N
A book weighs 4 N. When held at rest in your hands, the net force on the book is
0 N
When an object reaches terminal velocity its acceleration is
0 m/s^2
An apple weighs 1 N. The net force on the apple when it is in free fall is
1 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
10 times as much as the 1 kg book
The mass of a lamb that weighs 110 N is about
11 kg
A box is dragged without acceleration in a straight-line path across a level surface by a force of 13 N. What is the frictional force between the box and the surface?
13 N
A 20-N falling object encounters 4 N of air resistance. The magnitude of the net force on the object is
16 N
A girl pulls on a 10-kg wagon with a constant force of 20 N. What is the wagon's acceleration?
2 m/s^2
A tow truck exerts a force of 2000 N on a car, accelerating it at 1 m/s/s. What is the mass of the car?
2000 kg
A karate chop delivers a blow of 2300 N to a board that breaks. The force that acts on the hand during this feat
2300 N
Suppose the force of friction on a sliding object is 25 N. The force needed to maintain a constant velocity is
25 N
If you pull horizontally on a desk with a force of 150 N and the desk doesn't move, the friction force must be 150 N. Now if you pull with 250 N so the desk slides at constant velocity, the friction force is
250 N
When a woman stands with two feet on a scale, the scale reads 280 N. When she lifts one foot, the scale reads
280 N
How much does a 3.0-kg bag of bolts weigh
29.4 N
You pull horizontally on a 50-kg crate with a force of 450 N and the friction force on the crate is 250 N. The acceleration of the crate is
4 m/s^2
Two people pull on a rope in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope?
400 N
A person is attracted towards the center of Earth by a 440N gravitational force. The force with which Earth is attracted toward the person is
440 N
A woman weighing 550 N sits on the floor. She exerts a force on the floor of
550 N
As a 600-N woman sits on the floor, the floor exerts a force on her of
600 N
A sportscar has a mass of 1500 kg and accelerates at 5 meters per second squared. What is the magnitude of the force acting on the sportscar?
7500 N
How much force is needed to accelerate a 4.0-kg physics book to an acceleration of 2.0 m/s2?
8 N
A bag of sports equipment has a mass of 10.0 kilograms and a weight of
98 N
Earth pulls on the moon, and similarly the moon pulls on Earth. This is evidence that the
Earth and moon are simply pulling on each other. Earth's and moon's pulls comprise an action-reaction pair.
An object has a constant mass. A constant force on the object produces constant
acceleration
Whenever an object exerts a force on another object, the second object exerts a force of the same magnitude, but in the opposite direction to that of the first object.
always true
Friction
comes from microscopic bumps that act as obstructions to the object's motion. is the name given to the force acting between surfaces sliding past one another. acts in a direction that opposes the motion of an object.
Suppose a particle is accelerated through space by a constant 10-N force. Suddenly the particle encounters a second force of 10-N in a direction opposite to that of the first force. The particle
continues at the speed it had when it encountered the second force
As a care package falls from a high-flying stationary helicopter, its velocity increases and its acceleration
decreases
A bicycle and a parked car have a head-on collision. The force of impact is greater on the bicycle.
false
A given force exerted on a large mass produces a greater acceleration than the same force exerted on a small mass.
false
An astronaut weighs the same on Earth as in space.
false
If a hockey puck were to slide on a perfectly frictionless surface, it will eventually slow down because of its inertia.
false
The SI unit of force is the kilogram.
false
The SI unit of mass is the newton.
false
The acceleration of an object is inversely proportional to the net force acting on it.
false
The amount of matter in an object is its weight.
false
The force due to gravity acting on an object is its mass.
false
f you were to slide a hockey puck across a frictionless ice rink, there must be a horizontal force on it to keep it in motion.
false
Pressure is defined as
force per area
Accelerations are produced by
forces
According to Newton's third law, if you push gently on something, it will push
gently on you
An object following a straight-line path at constant speed
has zero acceleration
Forces always occur
in pairs
One object has twice as much mass as another object. The first object also has twice as much
inertia
How does acceleration of an object change in relation to its mass? It is
inversely proportional
The acceleration produced by a net force on an object is
inversely proportional to the mass of the object. directly proportional to the magnitude of the net force. in the same direction as the net force.
Suppose a cart is being moved by a force. If suddenly a load is dumped into the cart so that the cart's mass doubles, what happens to the cart's acceleration?
it halves
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
its weight
Compared to its weight on Earth, a 10-kg object on the moon will weigh
less
The law of inertia applies to
moving and non moving objects
Which has more mass, a kilogram of feathers or a kilogram of iron
neither they have the same mass
The unit of pressure is
newtons per square meter or pascals
A high school student hits a nail with a hammer. During the collision, there is a force
on the nail and also on the hammer
Friction is a force that always acts
opposite to an objects motion
The reason a tennis ball and a solid steel ball will accelerate at the same rate, in the absence of air resistance, is that
the ball with the larger force has a larger mass
Suppose you accidentally drive into a tree. Which of the following correctly describes the interaction between your car and the tree?
the car and the tree mutually exert equal and opposite forces on each other
A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. What is the reaction to this force?
the force the glove exerts on the ball
A heavy person and a light person parachute together and wear the same size parachutes. Assuming they open their parachutes at the same time, which person reaches the ground first?
the heavy person
An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass?
the one on the moon
As a ball falls, the action force is the pull of Earth's mass on the ball. What is the reaction to this force?
the pull of the balls mass on earth
A force of 3 N accelerates a mass of 3 kg at the rate of 1 m/s2. The acceleration of a mass of 6 kg acted upon by a force of 6 N is
the same
Aunt Minnie throws a rock downward, and air resistance is negligible. Compared to a rock that is dropped, the acceleration of the rock after it is thrown is
the same
Compared to its mass on Earth, the mass of a 10-kg object on the moon is
the same
A large truck and a small car traveling at the same speed have a head-on collision. The vehicle to undergo the greater change in velocity will be
the small car
A tennis ball and a solid steel ball with the same diameter are dropped at the same time. In the absence of air resistance, which ball has the greater acceleration?
they both have the same acceleration
A rocketship is pushed forward by gases that are forced out the back of the ship.
true
An astronaut has the same mass on Earth as in space.
true
The combination of all the forces that act on an object is called the net force.
true
The net force on an objecting falling at terminal velocity is zero
true
Whenever one object exerts a force on another object, the second object always exerts a force back on the first object.
true
The law of inertia states that an object
will continue moving at the same velocity unless an outside force acts on it.will continue moving in a straight line unless an outside force acts on it. that is not moving will never move unless a force acts on it. at rest will remain at rest unless acted on by an outside force.
If a horse pulls on a wagon at rest, the wagon pulls back equally on the horse. Can the wagon be set into motion?
yes because there is a net force acting on the wagon
The force required to maintain an object at a constant speed in free space is equal to
zero
After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals
zero since no force is needed to keep it going