Show:
Motion
Newton's Laws
Conservation Laws
Work and Machines
Center of Gravity
100
What is the speed of an object that covers 12 meters in 3 seconds?
4 m/s
100
State Newton's 1st and 2nd Laws.
1st: An object experiencing balanced forces will have a constant velocity. Objects experiencing unbalanced forces have changing velocities. 2nd: a = F/m
100
When we say "momentum is conserved," what does that mean?
An object or system's momentum won't change unless an outside force acts on it.
100
A certain object has 200 J of kinetic energy. An external force gives it a push, doing 200 J of work on the object to speed it up. How much kinetic energy does it have now?
400 J
100
Does an object's center of gravity have to be located on the object? (Give an example)
No - a donut, the weighted gymnast cutout, an open ladder
200
What's the difference between speed and velocity?
Velocity includes an object's direction of motion!
200
A bowling ball is rolling along a level floor. Describe its motion if friction is not a significant force.
Constant Velocity (no external forces)
200
When an object is falling, its potential energy from gravity is turning into kinetic energy. Is the object's TOTAL amount of energy changing?
No! (Not unless it encounters a lot of air resistance.)
200
How do simple machines make doing work easier?
They increase the distance over which the work is done, so that it requires less force.
200
An object will be balanced if its center of mass is located where?
Over the base that is supporting the object
300
A certain car is able to accelerate 10 m/s/s. How fast will it be going after 4.5 seconds?
45 m/s
300
What is the difference between mass and weight?
Weight is a force that depends on mass. Mass measures how difficult it is to accelerate an object.
300
Two balls fall to the ground. One is bouncy, the other is made of dough. Which will hit the ground with more force?
The bouncy one, since it experiences a greater change in momentum when it hits the ground
300
A certain 10 foot long ramp raises a person a height of 2 feet. What is the mechanical advantage of the ramp?
IMA=5
300
Why do people wave their arms around when the feel off balance or lift something heavy?
They are instinctively moving their center of mass so that it stays over their feet.
400
What's the difference between velocity and acceleration?
Velocity is a rate of change in position, while acceleration is a rate of change in velocity.
400
You attempt to put your fist through a piece of paper. Is it possible for you to hit the paper harder than the paper hits you?
No! According to Newton's 3rd Law, action-reaction force pairs are equal in magnitude.
400
What is it called when a force changes an object's energy?
Work!
400
Why does a very long lever require less force to pull than a short lever would?
The long lever is doing work over a larger distance
400
You have a meter stick balanced on your finger. Your friend places a small massive object on one end of the meter stick. Is it possible to balance the meter stick with the object on top of it? If so, how?
Yes; the center of gravity has shifted, though - move the meter stick so that your balancing finger is closer to the mass.
500
Projectile motion is a blend of two motions: one horizontal, the other vertical. Which one is the constant velocity motion? Which is the accelerated motion?
A projectile has constant horizontal motion and changing (accelerated) vertical motion.
500
Two kids are pushing in opposite directions on a 5 kg toy box. One pushes with 20 N of force, the other pushes with 10 N of force. How much will the box accelerate?
2 m/s/s in the direction of the larger force
500
A cannonball is fired out of a cannon. The cannonball goes flying forward. According to momentum conservation, the cannon must move backward. Will its speed be larger, smaller or the the same as the cannonball's speed?
The cannon's speed will be be smaller than the cannonball's, since its mass is bigger.
500
Even the best pulley system can't operate with an efficiency of 100%. Neither can any other machine. Why not?
When using a machine, energy is always lost to friction, heat, and other internal factors.
500
Your friend impresses you by being able to balance a pencil vertically on their finger. While the pencil is balanced, is it in stable, unstable, or neutral equilibrium?
Unstable equilibrium, since tipping left or right will lower the pencil's center of mass