Answer:
The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.
Explanation:
Given that,
Wavelength = 400 nm
Energy 
We need to calculate the longest wavelength of light that is capable of ejecting electrons from that metal
Using formula of energy


Put the value into the formula



Hence, The longest wavelength of light that is capable of ejecting electrons from that metal is 1292 nm.
Answer: Option (b) is the correct answer.
Explanation:
The force of gravity acting on an object helps in determining the weight of an object. But a place where there will be no gravity or have zero gravitational pull then it means the person will be weightless.
For example, force of gravity on moon is zero which means any object or person on moon will be weightless.
On the other hand, when a child is in the air as she plays on a trampoline then it means gravitational pull form the earth is acting on it. So, it will definitely has some weight.
Similarly, a scuba diver exploring a deep-sea wreck is under the ground where there will be force of gravity. Hence, it will also have some weight.
Thus, we can conclude that an astronaut on the Moon is the person who is weightless.
Answer:
∈=
Explanation:
Using the Gauss Law to determine the electric field of the net flux at the surface of the nucleus
∈
The P is the charge density and 'Eo' is the constant of permittivity in free space
to find P





So replacing
∈
∈=
Answer: The given statement is false.
Explanation:
According to Newton's third law of motion, every action has an equal and opposite reaction. So, when we apply force in one direction on an object then the object also applies a force in the opposite direction.
Hence, it is true that two forces in each pair of forces act in opposite directions.
For example, when we push a wooden box of 20 kg in the forward direction then the box will also apply a force in the opposite direction.
But the statement two forces in each pair can either both act on the same body or they can act on different bodies is false.
Answer:
- The initial speed of the truck is 21.93 m/s, and the initial speed of the car is 19.524 m/s
Explanation:
We can use conservation of momentum to find the initial velocities.
Taking the unit vector
pointing north and
pointing east, the final velocity will be


The final linear momentum will be:




As there are not external forces, the total linear momentum must be constant.
So:

As initially the car is travelling east, and the truck is travelling north, the initial linear momentum must be
so:
so

So, for the truck





And, for the car


