Laws of Motion Test

Result

Laws of Motion Test - 58

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Weekly Quiz Competition

Question 1
1 / -0

A cyclist moves along a circular track at 144 km $$h^{-1}$$.What angle must he make with the vertical if the track is 1 km long?

A
$$40^o$$

B
$$45^o$$

C
$$35^o$$

D
none

Solution
Question 2
1 / -0

The acceleration of a body may be doubled by doubling its:

A
mass

B
momentum

C
velocity

D
force acting on it

Solution

Acceleration $$a=\dfrac{Force}{mass}$$

Also $$a=\dfrac{\Delta P}{\Delta t \times m}$$, Where, $$\Delta P$$ is the change in momentum.

So to double the acceleration we need to $$double $$ the $$force $$ acting on it.
Question 3
1 / -0

An insect crawls up a hemispherical surface very slowly as shown in the figure. The coefficient of
friction between the surface and the insect is $$\dfrac { 1 }{ 3 } $$ If the line joining the centre of the hemisphere surface to the insect makes an angle $$\propto $$ with the vertical, the maximum possible value of $$\propto $$ is given by

A
$$cot\propto =3$$

B
$$tan\propto =3$$

C
$$sec\propto =3$$

D
$$cosec\propto =3$$

Solution
Question 4
1 / -0

A cone filled with water is whirled in a vertical circle of radius 4 m. What will be the time period of rotation so that water does not fall ?

A
4 s

B
6 s

C
2 s

D
1 s

Solution
Question 5
1 / -0

A track for a certain motor sport event is in the form of a circle and banked at an angle $$\theta$$. For a car driven in a circle of radius r along the track at optimum speed the periodic time is --------

A
$$\sqrt{\dfrac{r}{g}}$$

B
$$ 2 \pi \sqrt{r}{g}$$

C
$$ 2 \pi \sqrt{rg tan \theta}$$

D
$$ 2 \pi \sqrt{\dfrac{g tan \theta}{r}}$$
Question 6
1 / -0

Rahul is traveling in a bus on a straight road facing in the direction of the motion of the bus. If the bus starts accelerating in the same direction then Rahul will fall

A
Forward

B
Backward

C
Rightward

D
Leftward

Solution

The face is in the direction of motion so the force due to the acceleration of Bus will be opposite to motion that is opposite to face that is backward so he will fall backward.
The instant acceleration of the bus will be applied only to the foot of Rahul, while his upper body remains in the previous state, so Rahul will fall backward.
Question 7
1 / -0

Three blocks A,B and C are suspended as shown in the figure. Mass of each blocks A and C is m. If system is in equilibrium mass of B is M, then :

A
M=2 m

B
M < 2 m

C
M > 2 m

D
M=m

Solution
Question 8
1 / -0

A ball of mass 1 kg strikes a heavy platform, elastically, moving upward with a velocity of 5 m/s. The speed of the ball just before the collision is 100 m/s downwards. Then the impulse imparted by the platform on the ball is :-

A
15 N-s

B
10 N-s

C
20 N-s

D
30 N-s

Solution

According to the problem the mass of the ball is $$1\, kg$$

The velocity of the ball initially is $$5\, m/s$$ and the speed of the ball before collision is $$10\, m/s$$

Therefore the total speed of the ball $$= 10+5=15 \,m/s$$

Now we know that impulse is the change in momentum of ball.

Therefore impulse $$=15+15=30\,Ns$$
Question 9
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The breaking strength of a string is 55 kg wt. The maximum permissible speed of a stone of mass 5 kg which revolved in a vertical circle of radius 4 m with the help of is the string is g=10 $$ {s}^{2} $$.

A
$$

10 \mathrm{m} / \mathrm{sec}

$$

B
$$

15 \mathrm{m} / \mathrm{sec}

$$

C
$$

20 \mathrm{m} / \mathrm{sec}

$$

D
$$

25 \mathrm{m} / \mathrm{sec}

$$
Question 10
1 / -0

In the figure, at the free end of the light string, a force $$F$$ is applied to keep the suspended mass of $$18 $$\mathrm { kg }$$ at rest. Assuming

A
$$240 N$$

B
$$120 M$$

C
$$180 M$$

D
$$240 M$$

Solution

$$3T=180$$
or, $$T=60 N$$
Now, $$F=T=60 N$$
Therefore ,total force on ceiling is $$4T=240 N$$
Hence, Option $$A$$ is correct.