vocab
What is the definition of acceleration in physics?
Acceleration is the rate at which an object's velocity changes. This change can involve a change in speed, a change in direction, or both.
Why do you lunge forward when a car suddenly brakes, even though you're wearing a seatbelt?
Your body, due to inertia (Newton's First Law), wants to stay in motion at the same speed as the car. The seatbelt provides the necessary external force to overcome this inertia, stopping your body from continuing forward.
A magician pulls a tablecloth out from under dishes without disturbing them. Which of Newton's laws explains this phenomenon, and why?
Newton's First Law of Motion (Inertia) explains this. The dishes have inertia, meaning they resist changes in motion; since they were at rest, they tend to stay at rest even as the tablecloth is pulled quickly from under them.
What fundamental SI units combine to define one Newton (N) of force?
A Newton is defined as the force required to accelerate one kilogram of mass at a rate of one meter per second squared
A car accelerates from rest to 60 m/s in 10 seconds. What is its acceleration?
The car's acceleration is
What is the standard international (SI) unit for acceleration?
The SI base unit for acceleration is meters per second squared, or m/s²
If you push a small toy car and a real car with the same amount of force, which one accelerates faster, and why?
The toy car accelerates much faster because it has significantly less mass than the real car. According to
A 1500 kg car accelerates at
. What is the net force required to achieve this acceleration?
the net force is
A force is applied to a
object, causing it to accelerate at a rate of
. Calculate the magnitude of the force in Newtons.
The magnitude of the force is
An object is dropped from rest. Assuming negligible air resistance and
, what is its velocity after 2 seconds?
The object's velocity after 2 seconds is
In physics, an object is considered to be accelerating if it is speeding up, slowing down, or changing direction. What term describes an object that is slowing down?
An object that is slowing down is experiencing negative acceleration (sometimes called deceleration).
How does a swimmer move through the water?
The swimmer pushes backward on the water (action), and the water pushes forward on the swimmer with an equal and opposite force (reaction), propelling them forward
When a rocket launches, it expels hot gas downward. What is the action-reaction pair in this scenario?
The action is the rocket pushing the gas downward, and the reaction is the gas pushing the rocket upward with an equal and opposite force, propelling the rocket into space.
What is the weight of a
object on Earth, where the acceleration due to gravity is approximately
?
The weight of the object is
.
A bullet decelerates from 400 m/s to 300 m/s over a distance of 0.1 m. What is its constant acceleration?
The bullet's acceleration is
(deceleration of
An object moves at a constant velocity. What is its acceleration?
An object moving at a constant velocity has zero acceleration, because its velocity is not changing.
Is weight the same as mass?
No. Mass is the amount of matter in an object, while weight is the force of gravity on that mass
You are riding a bicycle and hit a rock, sending you flying forward off the bike. Which law best describes your motion after impact?
Newton's First Law of Motion (Inertia) applies here. Your body, in motion, tends to stay in motion forward, even as the bike stops, until another force (like gravity or the ground) acts on you.
A box is pushed to the right with
of force and simultaneously pushed to the left with
of force. What is the magnitude and direction of the net horizontal force acting on the box?
The net force is the difference between the forces:
. The direction is to the right, in the direction of the larger force.
A train accelerates at
for 5 seconds. If it started with an initial velocity of
, what is its final velocity?
The train's final velocity is
What term is used to describe a measure that includes both magnitude and direction, which applies to velocity and acceleration?
This type of measure is a vector.
A soccer ball sits still (Law 1). You kick it (Law 2), sending it flying. When it hits another player, they both move apart (Law 3). Explain this sequence.
The ball's stillness is inertia (Law 1). Your kick applies a force, causing acceleration
A constant net force of 100 N is applied to a 20 kg box. What happens to the box's acceleration if its mass is doubled to 40 kg (while the force stays the same)?
Applying
, the initial acceleration is
. If the mass doubles to 40 kg, the new acceleration becomes
. The acceleration is halved because acceleration is inversely proportional to mass (Newton's Second Law).
If you push against a stationary wall with a force of
, what is the magnitude of the force the wall exerts back on you?
According to Newton's third law, the wall exerts an equal and opposite reaction force of
back on you.
How long does it take for a rocket to accelerate from
to
with a constant acceleration of
?
It takes
for the rocket to accelerate.