Rotation

Q.

When does a body rotate ? State one way to change the direction of rotation of the body. Give a suitable example to explain your answer.

Q.

What do you understand by the clockwise and anticlockwise moment of force? When is it taken positive?

Q. A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to :

1. exert a large force on the ball.
2. decrease the rate of change of momentum.
3. increase the force exerted by the ball on hands.
4. increase the rate of change of momentum

Q.

What are collinear forces?

Q. Two forces can form a couple when they are

1. unequal and opposite forces acting along the same line.
2. equal and parallel forces acting along the same line.
3. unequal and parallel forces, acting along the same line.
4. equal and opposite forces not acting along the same line.

Q.

Define unbalanced forces.

Q.

How can you increase the turning effect of a force?

1. By lubricating the handle with oil and grease.

2. By decreasing the perpendicular distance between force and axis.

3. By increasing the perpendicular distance between force and axis.

4. By reducing the applied force.

Q.

The moment of force is assigned a negative sign. The turning tendency of the force will be

1. anticlockwise

2. clockwise

3. can be clockwise or anticlockwise

4. can neither be clockwise nor anticlockwise

Q.

A goalkeeper in a game of football pulls his hands backward after holding the ball shot at the goal. This enables the goalkeeper to

1. Exert larger force on the ball

2. Reduce the force exerted by the ball on the hands

3. Increase the rate of change in momentum

4. Decrease the rate of change in momentum

Q.

An object of mass 50 $kg$ accelerates from a velocity of 2.0 $m/s$ to a velocity of 10 $m/s$ in the same direction. What is the impulse provided to cause this acceleration?

1. 250 $Ns$
2. 400 $Ns$
3. 850 $Ns$
4. 2500 $Ns$

Q. The direction of rotation of a body pivoted at a point depends

1. only on the direction of force applied on the body.
2. on the magnitude of force on the body.
3. on both the direction and point of application of force on the body.
4. only on the point of application of force on the body.

Q. Which of the following options is incorrect regarding moment of force?

1. Conventionally, clockwise moments of force are taken as negative.
2. It is a vector quantity
3. Conventionally, clockwise moments of force are taken as positive.
4. The S.I unit of moment of force is N m

Q. Which of these quantities is measured in newton-second $\left(Ns\right)$?

1. Impulse
2. Power
3. Energy
4. Work done

Q.

We need to apply more force to turn the door when we apply the force close to the hinges. Give reason?

Q. A car with a steering wheel of radius $25cm$ is rotated with two anti-parallel forces of magnitude $5N$ each. Calculate the moment of the couple.

1. $250Nm$
2. $125Nm$
3. $1.25Nm$
4. $2.5Nm$

Q.

Three forces acting on a door handle as shown, how will the door handle move ?

1. Will turn clockwise
2. Will turn anti-clockwise
3. Will move left
4. Will remain stationary

Q. Which among the following forces is responsible for the raindrops falling downwards?

1. Electrostatic force
2. Magnetic force
3. Gravitational force
4. Frictional force

Q.

A body is moving with an initial velocity of $u$ and having constant acceleration $a$. The final velocity $v$ can be obtained by using which of the following equation of motion if a body covers a distance $s$.

1. $v^2=u^2+2as$

2. $s=ut+\frac{1}{2}a{t}^2$

3. $v=u+at$

4. $v^2=u^2+at$

Q.

Define balanced forces.

Q.

In order to rotate a bar pivoted at its mid point, we need to apply

1. two equal forces at the two ends, but in opposite directions

2. a small force exactly at the mid point where it is pivoted

3. a large force at any point on the bar

4. two unequal forces at the two ends, but in the same direction

Q. Two forces can cancel each other's effect if their magnitudes are .

1. equal
2. in the ratio 1:2
3. in the ratio 2:3

Q. Identify the point of application of force in order to open the door effectively.

1. 
2. 
3. 

Q.

A football player kicks a cricket ball, which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows down to stop because

1. The football player did not hit the ball hard.

2. The velocity of the ball is proportional to the force acting on it.

3. There is a force on the ball opposing its motion.

4. There is no unbalanced force on the ball and hence, it comes to rest.

Q.

Define balanced forces. [1 MARK]

Q. A body starts from rest at time $t=0$, accelerates uniformly and travels $320m$ in $4s$. Find its velocity at time $t=10s$.

1. $400m/s$
2. $200m/s$
3. $20m/s$
4. $40m/s$

Q.

In which direction does the force need to be applied when single pulley is used with a mechanical advantage greater than1 ? How can u change the direction of force applied without altering its ma

Q.

A corkscrew is used to open a cork sealed- bottle. Which pair of forces among the following produces a maximum turning effect ?

1. 
2. 
3. 
4. 

Q. A body is moving with an intial velocity of u, and no acceleration. Its velocity after t seconds is given by _______.

1. -u
2. ut
3. -ut
4. u

Q.

What is the principle of the moment?

Q.

Which class of a lever is always a force multiplier? Give example.

1. Class II; Crow bar

2. Class I; Crow bar

3. Class II; Wheel barrow

4. Class III; Crow bar

5. Class III; Wheel barrow