Work
Power
Direction of Force
Mechanical Advantage
Simple Machines
100
A woman is holding her water bottle up. Is she doing work?
No, because she isn't moving the water bottle.
100
What is one equation for Power?
P = W/t
P = Fv
100
What is the equation for work when you pull or push something across the floor at an angle.
W = FCosθd
100
What is the equation to calculate IMA?
IMA = de/dr
100
What simple machine is basically a wrapped inclined plane?
Screw
200
If the force is perpendicular to the motion of an object, is work being done on it?
No, the force has to be in the direction of the motion.
200
Two girls are running a marathon. They are doing the same about of work, but Girl B finishes just ahead of Girl A. Which girl had more power?
Girl B
200
What equation for work do you use if you are pushing something up some sort of incline?
W = mgSinθd
200
What is the mechanical advantage of a single fixed pulley?
1
200
What are two inclined planes?
a. doorstop
b. ax
c. screw
d. ramp
Ax
300
A woman starts to push a stroller across the room. What happens to the KE of the stroller?
It's increasing
300
A pitcher exerts 100.0 N of force on a ball with a power output of 2,500 W.
What is the velocity of the ball?
P = Fv
V = 25m/s
300
A sailor pulls a boat horizontally alongside a dock for 10.0 m with a rope angled at 40.0°. He uses a force of 100.0 N.
How much work does he do on the boat?
W=Fcosθd
766 J
300
Which machine has the smallest mechanical advantage?
Machine D
300
Give an example of a compound machine
Bicycle
Block and Tackle
Wheelbarrow
400
A man pulls a box with a force parallel to the ground. He pulls the box 10.0 m and does 5,000 J of work. What is the force?
W = Fd
F=500N
400
If a runner does 1,500 J of work over 10.0 s, then how much power does she have?
P = W/t
150 W
400
A motorboat travels directly east. During its trip, winds blow from directly north, directly south, and southwest. Which wind does work on the boat?
Southwest
400
An inclined plane is 20.00 m long and 5.00 m high.
What is the ideal mechanical advantage of this machine?
4
400
Instead of using a pulley, what other simple machine can be used to lift objects?
Ramp/inclined plane
500
If the people lift the masses below, which person is doing more work?
Person A: Mass: 100 Kg - Distance: 2.25 m
Person B: Mass: 200 Kg - Distance: 1.50 m
W = Fd and F = Mg
Person B does more work
500
A weightlifter lifts a 100 kg barbell 2.0 m from the ground in 2.0 s. What is the power of the lift?
W = Fd W = (100)(9.8)(2) = 1960J
P = W/t
Power = 1960/2 = 980 W
500
A 100.0 kg sailor climbs a 30 m rope ladder at an angle of 55.0° with the mast. How much work did he do?
W = mgSinθd
W = (100)(9.8) Sin(55) 30
W = 24,083 J
500
A sailor pushes a 100.0 kg crate up a ramp that is 3.00 m high and 5.00 m long onto the deck of a ship. He exerts a 650.0 N force parallel to the ramp.
What is the efficiency of the ramp?
W=Fd
Eff = Wo/We x 100%
Eff = 2940/3250 x 100 = 90%
500
Using a single fixed pulley, you apply a force of 20N to lift an object. What is the resistance force?
20 N