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6)
The question states that "X is measured with a percentage uncertainty of ±1 % of its value at all temperatures." meaning that the percentage uncertainty is unchanged, so A and B is eliminated.
then you need to apply some logic here, will the actual uncertainty get bigger as you approach 100 or 0?.
you can quickly do some math here, 100x1% = ±1 uncertainty while 0x1% = 0
so answer is C, least actual uncertainty when temperature close to 0
11)
The object hits the wall with a speed v, and rebounds with the same speed, but a velocity in the opposite direction.
Kinetic Energy does not depend on the direction of an object's velocity, just the magnitude of that objects velocity, i.e. the speed. Therefore, since the speed remains the same even after the collision, the Kinetic Energy of the object is conserved.
By the same logic applied above, we can say that the speed is conserved, so that option is eliminated.
Lastly, the mass of the object doesn't change, and therefore the mass also remains conserved.
By elimination, we can confidently say that the momentum of the object is the only value that is not conserved - momentum, unlike the other values, is a vector quantity; since the direction of the object's speed changes, the momentum also changes, and is therefore not conserved.
23)
We use F = kx
so we know k for P and Q is k and for R is 3k
--> Therefore total extension of P and Q = k + k = 2k and extension for P,Q and R = 1/2k + 1/3k = (5/6)^-1k = 6/5k
so F = W, k = 6/5k and x = ?
W = 6/5k * x
x = 5w/6k
29)
There should be more points on to which the light strikes so it's either B or C, but hence in C the lines are closer, there is more intensity
36)
Firstly the ammeter is directly connected with the fixed resistor so there is no change in readings.
And its obvious, when there are two resistors, if one resistor's resistance is increasing, so others resistor's resistance would decrease so R is proportional to V hence V decreases.
