Question

Q1) How much is the work done in 2 seconds if the power is 1 watt?
Q2) Name the unit of physical quantity obtained by the formula U/mg.
Q3) Give the example of a couple:-
a) wrench, b) spanner, c) jack
d)none.
Q4) A uniform metre rule rests horizontally on a knife edge at 70cm mark when a mass of 20gm is suspended from one end. What is the mass of the rule? ​

Answer 1

Explanation:

power=1 watt

time=2second

power = work/time

so, work= 1 *2

work= 2J

2) physical quantity obtained is height

U(Potential Energy) = mgh

h= U/mg

so, unit of h is metre

3) spanner

4) Let the mass of the rule be m g

Rule is uniform metre= 100cm

Mid-point= 50cm

Mark where it rests horizontally = 70cm

mass suspended from one end= 20gm

Clockwise moment= Anticlockwise moment

(70-50)*20= 50*m

20*20= 50*m

400/50=m

8=m

so, mass of rule is 8g