Motion
What is the formula for acceleration?
change in velocity over time
What is friction?
A force that resists motion
What law is also known as the law of inertia
Newton's 1st law
What is momentum?
The mass of an object times its velocity.
A train travels at 100 km/h east to reach a town in 4 hours. The train then reserves and heads west at 50 km/h for 4 hours. What is the train's position now?
The train is 200 km east of where it started.
How does acceleration look on a position vs. time graph?
The position vs. time graph is a curve where there's acceleration.
Weight is a force that depends on what?
Mass and gravity
What are the three Newton's laws?
Newton's 1st Law is an object will stay at rest unless acted by an unbalanced force. Newton's 2nd law is acceleration is force divided by mass. Newton's 3rd Law is for every action force there is a reaction force equal in strength and opposite in direction.
What is the law of conservation of momentum?
A law that states that as long as interacting objects are not influenced by outside forces, the total amount of momentum is constant.
A sailboat moves at 1m/s. A strong wind increases its speed to 4m/s in 3 seconds. What is the accelration?
1m/s^2
What is instantaneous speed?
The actual speed of a moving object at any moment.
What are the four elementary forces?
Strong nuclear force, electromagnetic force, weak force, and gravity.
Why is Einstein faster than buffalo when it comes to skateboarding?
Einstein has much less mass so he has more acceleration, therefore his speed is always greater.
What happens when two objects collide?
They exert equal and opposite forces on each other.
A rat weighing 40 N stands on a chair. If the normal force on each of the rat's arms is 12 N, what is the normal force on each front paw.
8 N
What is free fall? What is acceleration due to gravity?
Free fall is accelerated motion that happens when an object fails with only the force of gravity acting on it. Acceleration due to garvity is the value of 9.8m/s^2 on Earth, represented by g.
What are contact forces and "At-a-distance" forces. What are some examples of each?
Contact forces is transmitted by matter directly touching other matter. Examples are friction. normal force, tension, air resistance, and spring. At-a-distance forces occur when space is empty of matter so the force cannot be a contact force. Examples are gravity, electricity, and magnetism.
It takes more force to accelerate a Libby 8th grade backpack than a regular school 8th grade backpack. What Newton's Law best applies for this situation?
Newton's 2nd law
What is the relationship between total amount of momentum in the system before and after the collision?
It will be the same
Sally and the skateboard on which she is standing have a combined mass of 60 kg. Sally throws a 1-kh rock forward at 20 m/s. At which speed will she roll backward
0.33m/s
What is a projectile? What is an example?
projectile s an object moving through space and affected only by gravity, and the shape is a parabola. An example is kicking a soccer ball.
What is tension, extension, and compression
Tension is a pulling force that acts in a rope, string, or other object. Extension is a "stretch" or increase in size. Compression is a "squeeze" or decrease in size.
Why don't action and reaction forces just cancel each other out?
They act on different objects
How do rockets and jet planes use the law of conservation of momentum?
In a process called jet propulsion, a jet moves forward when the engine pushes exhaust air at a very high speed out of the back of the engine. The momentum lost by the air going backward is compensated by the momentum gained by the jet moving forward.
An astronaut in space throws a 2kg wrench away from him at a speed of -10m/s. If the astronaut's mass is 100kg, what speed does he move backward after throwing the wrench?
0.2 m/s