KE and Frame of Reference

Q. Consider two observers moving with respect to each other at a constant speed $v$ along a straight line. They observe a block of mass $m$ moving a distance $l$ on a rough surface. Then which of the following quantities will be same as observed by the two observers:

1. kinetic energy of the block at time $t$
2. work done by friction
3. acceleration of the block
4. total work done on the block

Q. Determine the time in which the smaller block reaches the other end of bigger block in given figure.

1. 4 $s$
2. 3 $s$
3. 8 $s$
4. 2.19 $s$

Q. Consider two observers moving with respect to each other at a constant speed $v$ along a straight line. They observe a block of mass $m$ moving a distance $l$ on a rough surface. Then which of the following quantities will be same as observed by the two observers:

1. kinetic energy of the block at time $t$
2. work done by friction
3. total work done on the block
4. acceleration of the block

Q. In an experiment, the refractive index of glass was observed to be $1.45,1.56,1.54,1.44,1.54$ and $1.53$. Calculate Mean absolute error.

Q. The order of frequency used in satellite communications is:

1. $1-40$ GHz
2. $1-40$ MHz
3. $1-40$ KHz
4. Depends on the distance between antennas

Q. When the orange light passes from air ($n=1$) into glass ($n=1.5$), what is its new wavelength?

1. $4\times {10}^{-7}m$
2. $4\times {10}^{-6}m$
3. $2.5\times {10}^{-7}m$
4. $6\times {10}^{-7}m$
5. $9\times {10}^{-7}m$

Q. Consider two observers moving with respect to each other at a constant speed $v$ along a straight line. They observe a block of mass $m$ moving a distance $l$ on a rough surface. Then which of the following quantities will be same as observed by the two observers:

1. kinetic energy of the block at time $t$
2. work done by friction
3. total work done on the block
4. acceleration of the block

Q. The frequency band for satellite communication is

1. 88-108 MHz
2. 3.7-6.425 GHz
3. 420-890 MHz
4. 540 -1600 kHz

Q. Consider two observers moving with respect to each other at a constant speed $v$ along a straight line. They observe a block of mass $m$ moving a distance $l$ on a rough surface. Then which of the following quantities will be same as observed by the two observers:

1. kinetic energy of the block at time $t$
2. work done by friction
3. total work done on the block
4. acceleration of the block

Q. Suppose that the speed of sound in air at a given temperature is 400 m/sec. An engine blows a whistle at 1200 Hz frequency. It is approaching an observer at the speed of 100 m/sec. What is the apparent frequency as heard by the observer [MP PMT 1991]

1. 1200 Hz
2. 1500 Hz
3. 600 Hz
4. 1600 Hz

Q. A sound source $A$ and a reflecting surface $B$ move directly toward each other.
Relative to the air, the speed of source $A$ is $29.9m/s,$ the speed of surface $B$ is $65.8m/s,$ and the speed of sound is $329m/s$.
The source emits waves at frequency $1200Hz$ as measured in the source frame.
In the reflector frame, what is the frequency of the arriving sound waves?

Q. Kinetic energy does not depend on frame of reference.

1. True
2. False

Q. Kinetic energy does not depend on frame of reference.

1. True
2. False

Q. Kinetic energy does not depend on frame of reference.

1. True
2. False

Q. The refractive index ($\mu$) of glass is found to have the values $1.49,1.50,1.52,1.54and1.48$. Calculate absolute error is each measurement.

1. $\Delta n_5=1.51-1.48=+0.03$
2. All of these
3. $\Delta n_4=1.51-1.54=-0.03$
4. $\Delta n_3=1.51-1.52=-0.01$