Science - HELP!!!!!?

Question

Please answer as many as you can. Thank you SO much! I really REALLY appreciate it :)

1. A fixed, single pulley that is used to lift a block does which one of the following?

• doubles the force required to lift the block

• decreases the force required to lift the block

• makes the block easier to lift by changing the direction of the force needed to lift it

• decreases the force required and changes the direction of the force required

2. A machine that changes only the direction of a force has a mechanical advantage of ____.

• 1

• 2

• 10

• 100

3. Most materials ____ when they are heated.

• condense

• freeze

• expand

• contract

4. An inventor claims to have built a machine that can produce 120 J of work with an input of 110 J. Would you believe the inventor's claim? Why or why not?

Answer 1

1. the 3rd one

2.?

3.the 3rd one

4.?

by the way, I'm in grade seven

Answer 2

Easier to lift by changing the direction

2, just changing the direction -- mec adv. = 1

3. Expan

4.Input = output minus friction or something is rotten. Concervation of angular momentum or whatever will apply. Usually people will end up not considering the effect of gravity on the moving object.

Answer 3

1.  

In physics equations most pulleys are considered frictionless( so it doesn't change the actual force).  Rather, by using a single pulley we can make lifting easier because we break the force up into its horizontal and vertical components.  Using angles we can manipulate how much of the force is shifted to a particular component making it easier to move.

2.

Force is a vector.  It has a magnitude and a direction.  If you change the direction the magnitude stays the same.  Thus if we have a given force we call that force 100% or 1x.  If we change its direction then the direction changes but we still have 1x of the force.  Thus the answer is 1.

3.

When materials are heated they expand.

When they are cooled they contract.

This is because of kinetic energy.

When a material is heated the molecules move faster causing an increase in kinetic energy.  This cause more collisions of the particles.  Due to this movement the molecules tend to deform the material by expanding them.

4.

Joules are a unit of energy.  Machine often provide an easier way of doing something by converting mechanical energy into motion.  Like the pulley that is used to lift the incredibly large stone.  You aren't actually doing all lthe work, you are adding a little bit of energy to the system and the machine is converting it in a way that allows for alot more energy output.

So yes it might be possible.

Answer 4

1.) makes the block easier to lift by changing the direction of the force needed to lift it

2.) 1

3.) expand

4.)No, you can never have more output work than input work in a machine.

I GOT AN 100% ON MY TEST!!!

Answer 5

1. b, i believe (90% sure)

2. 1 (80 % sure)

3. expand (100%sure)

4. no, bc you still must do same amount of work to move an object (95% sure)