1
COMEDK 2021
MCQ (Single Correct Answer)
+1
-0

Newton's second law of rotational motion of a system particles having angular momentum L is given by

A
$${{dp} \over {dt}} = {\tau _{ext}}$$
B
$${{dL} \over {dt}} = {\tau _{{\mathop{\rm int}} }}$$
C
$${{dL} \over {dt}} = {\tau _{ext}}$$
D
$${{dL} \over {dt}} = {\tau _{{\mathop{\rm int}} }} + {\tau _{ext}}$$
2
COMEDK 2021
MCQ (Single Correct Answer)
+1
-0

The motion of a particle of mass $$m$$ is described by $$y = ut + g{t^2}$$. The force acting on the particle will be

A
zero
B
$$4~mg$$
C
$$3~mg$$
D
$$2~mg$$
3
COMEDK 2021
MCQ (Single Correct Answer)
+1
-0

When a car of mass $$m$$ is moving with speed $$v$$ along a circle of radius $$r$$ on a level road, the centripetal force is provided by $$f$$, where $$f$$ denotes

($$\mu_s$$ $$\to$$ coefficient of friction, N $$\to$$ normal reaction)

A
$${{m{v^2}} \over r} = f \le {\mu _s}N$$
B
$$f < {\mu _s} = {{m{v^2}} \over r}$$
C
$$f = {\mu _s}N = {{m{v^2}} \over r}$$
D
$$f = {\mu _k}N = {{m{v^2}} \over r}$$
4
COMEDK 2021
MCQ (Single Correct Answer)
+1
-0

Ba-122 has half-life of 2 min. Experiment has to be done using Ba-122 and it takes 10 min to set up the experiment. It initially 80 g at Ba-122 was taken, how much Ba was left when experiment was started?

A
2.5 g
B
5 g
C
10 g
D
20 g
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