Motion, speed, and acceleration
An airplane is getting ready to take off. It begins at 0 m/s. It’s final speed is 40 m/s. It took 5 seconds for the plane to go from its initial speed to its final speed. What was the airplanes acceleration?
The airplanes acceleration is 8 m/s squared
What is a force?
A force is a push or a pull
Finish Newton’s third law of motion:
For every action, there is an...
Equal but opposite reaction.
How do you know if work is being done?
When an object moves in the same direction as the force
A certain car can accelerate from rest to 27m/s in 9 seconds. Find the car's acceleration.
acceleration = final speed - initial speed / time
so 27 - 0 / 9 = 3 m/s^2
Suppose a runner runs 70 meters in 2 hours and then runs another 14 meters the next hour. What is the average speed of the runner?
The average speed is 28 meters per hour
How can you find the net force if two forces are acting in opposite directions?
You can subtract the two forces to determine the net force.
What is the law of conservation of momentum?
The total momentum of objects that interact does not change
If an object does not move, is work being done?
What net force is needed to accelerate a 50kg cart at 15 m/s?
force = mass x acceleration so 50 x 15 = 750 N
What is the speed of an object that traveled 50 meters in 5 seconds?
10 meters per second
How do balanced forces affect an objects motion? How do unbalanced forces affect an objects motion?
Balanced forces acting on an object will not change the objects motion. Unbalanced forces acting on an object will cause the object to start moving, stop moving, or change directions.
Explain Newton’s second law of motion which states:
Acceleration depends on the objects mass and the net force acting on the object.
The greater the force, the greater the acceleration or the greater the mass, the lower the acceleration.
What is a machine?
A machine is a device that allows you to do work in a way that is easier.
Which has more momentum: a 225kg dolphin swimming at 5m/s, or a 300kg manatee swimming at 1.5m/s? Show formula, all work and a sentence for full credit.
momentum = mass x velocity
momentum of the dolphin = 1125 kg x m/s
momentum of the manatee = 450 kg x m/s
The dolphin has more momentum
What is a reference point?
A reference point is a place or object used for comparison to determine if something is in motion
What is friction?
Friction is the force that 2 surfaces exert on each other when they rub against each other
An object at ________ will remain at __________. An object in _________ will remain in ________ at a constant _________ unless something acts on it.
Rest, rest. Motion, motion, velocity.
What are the three ways that a machine makes work easier?
By changing force, distance, or direction
Your laundry basket weighs 35N and your room is 4m above you on the second floor. It takes you 8 seconds to carry the laundry basket up. What is your power? Show formula, all work and a sentence for full credit.
power = force x distance / time
power = 17.5 W
How can you tell if an object is in motion?
An object is in motion if it changes position relative to a reference point
What are the four types of friction?
Static, sliding, rolling, and fluid
What is inertia? Provide an example
Inertia is the tendency of an object to resist a change in motion. An example would be when a car slams on its breaks and the person keeps moving forward.
What are the 6 kinda of simple machines?
An inclined plane, a wedge, screws, levers, wheel and axle, and pulleys
You do 30 Joules of work while using a hammer. The hammer does 25 Joules of work on a nail. What is the efficiency of the hammer? Round to the nearest whole percent.
Efficiency of the hammer is 83%