Answer

Answer is (c) It always goes away from the earth

Explanation:

To move away from earth Object’s acceleration should be more than the acceleration due to gravity. To escape from gravity only moving along a straight path is not enough hence option (C) is a wrong statement.

According to the third law of motion, action and reaction (a) always act on the same body (b) always act on different bodies in opposite directions (c) have same magnitude and directions (d) act on either body at normal to each other.

Answer

Answer is (b) always act on different bodies in opposite directions

Explanation:

Newton’s third law states that “For every action there is equal and opposite reaction”. Hence answer is b)

Answer

Answer is (b) reduce the force exerted by the ball on hands

Explanation:

Pulling hands backwards will help goalkeeper to reduce the momentum of the ball which inturn reduces the force of the ball exerted on goalkeeper’s hands.

Answer

Answer is (c) to resist any change in its state of motion

Explanation:

Inertia is the property which resists the state of motion of an object. Object remains in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.

Answer

Answer is (a) accelerated

Explanation:

If the motion of train is uniform the coin would have fallen in his hand. If the motion is retarded coin would have fallen ahead of him. Since the coin falls behind the person motion of the train is accelerated.

Answer

Answer is (b) $0 {N}$

Explanation:

Here the friction is opposing the force hence no force is required to keep the object in uniform motion. Hence the answer is $0 N$.

Answer

Answer is (c) momentum

Explanation:

Velocity of hot gases coming out of rocket provided large momentum in opposite direction which makes the rocket move upwards. Here the conservation of momentum takes place.

Answer

Answer is (b) move forward

Explanation:

On applying brakes water tanker comes to rest but water will be in motion this makes the water to come forward.

Answer

Inertia depends on the mass of the object. For the solids with same size and volume inertia is determined by its mass. Hence steel will have highest inertia.

Answer

Yes the balls start rolling in the direction of train was moving.. When brakes are applied, train will come to rest and balls try to attain rest because of inertia balls remain in motion and they began to roll. Since the mass between two balls are not same inertia of iron ball is greater than the inertia of rubber ball. Hence rubber ball rolls faster than iron ball.

Answer

The momentum of the bullet depends on the backward momentum of the rifle. Since momentum of lighter rifle is more than the heavier rifle, bullet fired from lighter rifle hurts the shoulder more.

Answer

When cart moves on the road it has to encounter the friction. In order to keep the cart moving horse should overcome the friction. Hence it continues to apply the force.

Answer

If external force did not act on the system momentum of that system remains constant. In the give case change in velocity is due to gravitation force of the earth.

Answer

Given, $m=50 g$

$F=$ ?

Force $=$ mass $\times$ acceleration

$=\dfrac{50}{1000} \times 10=0.5 N$

velocity $=80 ms^{-1}$.

Velocity decelerates due to the friction of the floor with itself and comes to rest after 8 seconds.

$a=\dfrac{\text{ Change in velocity }}{\text{ Time }}=\dfrac{0-80}{8}$

$=-10 m / s^{2}$

The negative sign indicates that the frictional force exerted opposes the motion of the ball. Now, using Newton’s relation,

Force $=$ mass $\times$ acceleration

$=\dfrac{50}{1000} \times-10$

$=-0.5 N$

Answer

Force $=$ mass $x$ acceleration

$F=ma$

$a=f / m$

When mass is doubles force is halved $m$ becomes $2 m$ and $f$ becomes $f / 2$

$a_2=\dfrac{f}{4 m}$ or $\dfrac{a 2}{a 1}=\dfrac{f}{4 m}+\dfrac{f}{m}=\dfrac{1}{4}$

acceleration reduces to $\dfrac{1}{4}$ th

Answer

Distance between them will increase. Before throwing ball momentum of both of them will be zero. To conserve the momentum person who throws the ball moves backward. Person who catches the ball experiences a net force while catching the ball and he moves backwards.

Answer

Water sprinkler works on third law of motion. When water comes out of sprinkler an equal and opposite force is exerted. This will make the sprinkler rotate.

Answer

(i)

$ \begin{gathered} m=10 g \\ =\dfrac{10}{1000} kg u \\ =103 m / s \\ v=0 \end{gathered} $

(ii) $v=u+at$

$ 0=10^{3}-10^{7} t $

$ \begin{aligned} & 10^{7} t=10^{3} \\ & t=10^{3} / 10^{7} \\ & =10^{-4} s \end{aligned} $

Answer

$F=m a=kg m s^{-2}$

This unit is also called newton. Its symbol is $N$.

$m 1=\dfrac{f}{a 1}=\dfrac{5}{8} kg$

$m 2=\dfrac{F}{a 2}=\dfrac{5}{24} kg$

$m=\dfrac{5}{8}+\dfrac{5}{24} kg=\dfrac{5}{6} kg$

Acceleration produced in $M$

$a=\dfrac{f}{m}=\dfrac{5}{5 / 6}=6 ms^{-2}$

Answer

The quantity of motion of a moving body is called momentum. It is measured as product of mass and velocity.

Momentum $=$ mass $\times$ velocity

SI unit of momentum is $kg m s^{-1}$

Force $=$ Rate of change in momentum

(1)

(2)