Friction
Friction that occurs when something is moving is called
in a vacuum, feather and a bowling ball will fall at the same or different rates?
same
A 4 kg object is moving at 5 m/s. It has a kinetic energy (KE) of ?
KE = 1/2 mv2
KE = 1/2 (4)(5)2
KE = 50 J
If I pull my friend 10 m in a wagon, exerting a force of 50 N in the direction he moves, I have done how much work?
500 J
The weight of an object that has a mass of 10 kg is
98 N
Friction that occurs when trying to initiate movement is called
static friction
newton’s second law is
F=ma
A 10 kg ball sitting on a cliff that is 10 m high has a potential energy (PE)of?
980 J
the amount of work done each second is ?
power
Which is the weakest of the fundamental forces?
gravitational force
Friction is always in this direction
opposite motion
your friend pushes a car with a force of 50N. If its mass is 25 kg, what will be its acceleration?
a = 2 meters per second squared
An object has a KE of 10 J. If you double its velocity, what is the new KE?
40 J
because KE depends on velocity squared
so double velocity (multipy it by two) means the new KE is multiplied by 22 = 4
A machine makes work _?_ to do
easier
Which is the strongest of the fundamental forces?
strong force
If a man pushes on a motionless object with a force of 50 N, and the static friction force acting on the object is 50 N, will the object remain motionless, or begin to accelerate?
it will remain motionless
If your friend pushes on a 25 kg car with a force of 50 N, and you help by pushing with a force of 50 N, what is the car’s acceleration?
What is the total mechanical energy of an object?
sum of KE and PE
KE+PE
A long gentle ramp requires (more or less?) force to move an object than a shorter, steeper ramp
less
Two objects sit 1 m apart. They exert a gravitational force of attraction of 36 N on each other. When you move them 2 m apart, they now experience a gravitational force of ?
9 N
we divide by distance squared, so the same two objects that have the distance between them doubled (multiplied by 2) would have the old gravitational force divided by 22= 4. So divide 36 by 4
If a man pushes on a motionless object with a force of 80 N, and the static friction force acting on the object is 50 N, will the object remain motionless, or begin to accelerate?
it will accelerate
Newton’s third law, action-reaction
The 10 kg ball sitting on the 10 m high cliff begins to fall. What is its KINETIC energy when it is halfway down?
490 J
How much work does it take to lift a 100 lb weight straight up a distance of 4 ft?
400 ft lb
Two objects sit 1 m apart. They exert a gravitational force of attraction of 36 N on each other. When you move them 3 m apart, they now experience a gravitational force of ?
4 N
we divide by distance squared, so the same two objects that have the distance between them tripled (multiplied by 3) would have the old gravitational force divided by 32= 9. So divide 36 by 9