Question

1. Suppose you have two blocks initally at rest connected by a string. You exert a force on block A such that it begins to pull block B. Which blocks have work being done on by your hand?

a) An object is falling down a ramp. It reaches the botton with a speed of Vbottom, how does V botton change if you double the mass? How does it change if you double the height of the ramp? What if you performes this experiment on the moon?

b) Explain what is work (physics term)? What is kinetic energy? The relationship between the work done by the net force on the object and kinetic energy of object.

c) How do you know the work-energy theorem is true? (hint: describe clearly how it works in yourexperiment or in real life)

Answer 1

1)

Work done by your hand is clearly on the pulling block A

a) Vbottom = sqrt(2*g*h)

Vbottom does not depend on mass

So no change in Vbottom if we double the mass

if height of the ramp is doubled then Vbottom increases by sqrt(2) times

if it was performed on moon then Vbottom = sqrt(2*(g/6)*h)

then decreases by a factor sqrt(6)

B) Work : if a force is applied to displace a body then we can say that work is done

kinetic energy : the energy possessed by virtue of the motionof the body

by work energy theorem

Work done by net force = change in kinetic energy of the object

C) Suppose the a body is dropped then the amount of work done by the gravitational force is Wg = 0.5*m*v^2

here v is the speed with which the body is hitting the ground