Acceleration is absolute; it remains the same across all inertial frames.
About 2.0 × 10³ m/s².
It can refer to both a unit of force (pound-force) and a unit of mass.
The 'butterflies in the stomach' sensation, similar to free fall.
Friction forces exerted by water and air.
In the absence of a net external force, a body in motion continues to move at constant velocity.
It acquires a spontaneous acceleration toward the rear of the truck.
17 m/s².
2.7 × 10² N.
2.5 × 10^5 N and 1.0 × 10^5 N.
It is directly proportional to the force vector and inversely proportional to the mass of the body.
Any reference frame in uniform translational motion relative to an inertial frame is also inertial.
It will not continue moving, which does not contradict Newton's First Law because friction is acting on it.
By applying the same force to different masses and observing the resulting accelerations.
1.2 × 10⁷ N.
The downward pull of gravity (weight) and the upward pressure of the water (buoyancy).
F_net,x = F_1,x + F_2,x.
The direction of acceleration is determined by the resultant of the two forces.
Weight.
Newton (N).
It is directly proportional to the mass of the body.
The resistance that solid bodies offer to interpenetration.
The normal force is 50 N.
It is equally valid to regard either atom as 'acting' or 'reacting'.
The weight of the box (downward) and the normal force from the floor (upward).
We feel heavy, as if the floor is pushing harder on our feet.
By comparing the forces acting on them using a beam balance.
4100 kg.
Weight is the downward pull that gravity exerts on a body and is proportional to its mass.
Because they cancel each other and do not contribute to the net force.
No, weightlessness is impossible, but it can be simulated in a freely falling reference frame.
Weight depends on the gravitational environment and can vary with location.
Whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former.
Both are normal forces when perpendicular to the wall.
Internal forces.
The acceleration will be 8 m/s².
Pound-force (lbf).
F_1,x = 2.5 × 10^5 N × cos(30°).
Their surfaces begin to repel each other.
60 N.
It remains at rest.
About 0.034 m/s².
The single force that has the same effect as the combination of the individual forces.
By taking the square root of the sum of the squares of the components.
3.1 × 10^5 N.
It continues to move with constant velocity, as though no force is acting on it.
w = mg, where g is the acceleration due to gravity.
No, it is not massless; it still has mass.
No, it is equally valid to regard either force as the action or the reaction.
Because the mass of the Earth is so large that a force of only 2 N produces negligible acceleration.
Galileo Galilei.
Dynamics.
Yes, it is an inertial reference frame because the diver is in free fall and not experiencing any acceleration relative to gravity.
The Law of Inertia.
A push or pull exerted on a body, which has both magnitude and direction.
1 × 10⁴ N.
The pulls from the two tugboats and the frictional resistance of the water.
F_net = F_1 + F_2.
The net force is the sum of the forces exerted by both tugboats.
Gravity can act over distances without direct contact, unlike most everyday forces.
Compressional force (normal force) and friction force.
Mass is intrinsic and constant regardless of location; weight is extrinsic and varies with gravity.
On Jupiter, where the acceleration due to gravity is 24.8 m/s².
The normal force exerted by the box downward on the floor.
The force must counteract the person's weight and provide the necessary upward acceleration.
It becomes a non-inertial reference frame due to the change in direction.
The force is directed forward.
1 N = 1 kg * 1 m/s².
3.3 × 10⁷ N.
The Superposition Principle for forces.
Smaller than their weight.
By expelling exhaust gases, which push the rocket forward.
The body and the forces needed to formulate the equation of motion of the body.
They will accelerate downward due to gravity.
The laws of motion and the Law of Universal Gravitation.
The relationship between the force acting on a body and the acceleration caused by that force.
No, it is not inertial due to the Earth's rotation causing centripetal acceleration.
It becomes a non-inertial reference frame due to the acceleration.
The acceleration will be 2 m/s².
Both accelerate downward at the same rate, so the ball does not accelerate relative to the player.
It would be nearly zero, making the body weightless.
The action force of the hand on the wall and the reaction force of the wall on the hand.
F = ma, where F is the force, m is the mass, and a is the acceleration.
Yes, the push will accelerate the sailboat.
Electron: 9.11 × 10⁻³¹ kg, Proton: 1.673 × 10⁻²⁷ kg, Neutron: 1.675 × 10⁻²⁷ kg.
It states that the net force determines the acceleration of the body.
The angle with the x-axis, calculated using the tangent of the y and x components.
The friction force is assumed to be zero.
The player perceives the weight of the ball and his own body as zero.
The support balances the downward weight force, preventing downward motion.
The normal force on the first book becomes 100 N, and the normal force exerted by the first book on the second is 50 N.
They push the body forward when a force is exerted backward against a surface.
Because they act on the same object (the box) and are not exerted on each other.
In the absence of a net external force, a body at rest remains at rest.
No net external force acting on it.
Inertial reference frames.
Yes, it does not contradict; it is due to friction acting on the ball.
The newton (N).
3.5 × 10²² N.
10⁻¹⁹ N.
The net force is upward, equal to the weight of the elevator.
A vector quantity.
530 N.
Larger than their weight.
It exerts a frictional resistance, hindering propulsion.
A diagram that shows a body and all the external forces acting on it, excluding the reaction forces it exerts.
Devices such as brakes and safety locks to prevent free fall.
Inertia.
The law is valid only in inertial reference frames where clocks are correctly synchronized.
68000 N.
About 6.0 × 10⁻¹¹ kg.
The acceleration produced is the same as that produced by a single net force given by the vector sum of the individual forces.
They confirm that the net force on a planet is the vector sum of all gravitational pulls exerted by the Sun and other planets.
30° and 15°.
Through slight compression of the wall's material, which behaves like miniature springs.
Because they act on different bodies.
The push of the wall on your hand also makes a corresponding angle, involving both normal and friction forces.
Yes, it is an inertial reference frame because it is not accelerating.
B) The reference frame of a bird descending at constant velocity.
Yes, it is an inertial reference frame.
Force is defined as F = m * a, where m is mass and a is acceleration.
Using a spring balance.
The net external force is in the direction of the acceleration.
They are equal in magnitude and opposite in direction but act on different bodies.
If the push of your hand on a wall is 60 N, the wall pushes back with 60 N in the opposite direction.
The net force in the y direction is the sum of the y components of the individual forces.
F_2,x = 1.0 × 10^5 N × cos(15°).
The push that one surface exerts on another when they are in contact.
It is perpendicular to the wall.
The force of gravity is 9.81 N (downward) regardless of its motion.
By pushing backward on the ground, which then pushes him forward.
The gravitational pull of the Earth on an apple in free fall, and the apple's pull on the Earth.
The net force on the parachutist is zero, but there are still forces acting on them.
By flying along a parabola, imitating the motion of a frictionless projectile.
When the rocket engines cut off and the spacecraft coasts through empty space.
By pushing backward on the ground with its wheels, which pushes it forward.
For every action, there is an equal and opposite reaction.
