A drop of mass 2.0 g falls from a cliff of height 1.0 km. It hits the ground with a speed of 50.0 m/s. The work done by resistive force is

1. -10j
2. -12.50j
3. -15.5j
4. -17.50j
solution:- I think change in kinetic energy can give me work done. But how to get resistive force.

According to work energy theorem

W done by gravity +W done by resistive force =1/2 mv^2
W done by gravity = mgh = 2*10^-3*10*1000=20J
1/2mv^2= 1/2*2*10^3*(50)^2=2.5J
Thus, Work done by resistive force=1/2mv^2-work done by gravity
=20-2.5 J
= 17.5 J ( It can take negative value since it is a resistive force acting opposite to the direction of motion of the drop)
Hope you get it !!!

To determine the work done by the resistive force, you can use the work-energy principle. According to this principle, the net work done on an object is equal to the change in its kinetic energy.

In this case, the work done by the resistive force can be calculated using the formula:

Work = Change in Kinetic Energy

The initial kinetic energy (KEi) of the drop of mass 2.0 g can be calculated as:

KEi = (1/2) * m * v^2
= (1/2) * 0.002 kg * (50.0 m/s)^2
= 0.025 J

The final kinetic energy (KEf) of the drop can be calculated as:

KEf = (1/2) * m * v^2
= (1/2) * 0.002 kg * (0 m/s)^2
= 0 J

The change in kinetic energy (ΔKE) is given by:

ΔKE = KEf - KEi
= 0 J - 0.025 J
= -0.025 J

Since the kinetic energy decreases, it means that the work done by the resistive force is negative. Thus, the correct answer is:

2. -12.50 J

To find the work done by the resistive force, you need to calculate the change in kinetic energy of the drop as it falls from the cliff. The resistive force is caused by air resistance.

First, let's calculate the initial kinetic energy of the drop as it falls from the cliff. We can use the formula for kinetic energy:

Kinetic energy = (1/2) * mass * velocity^2

Given:
Mass of the drop (m) = 2.0 g = 0.002 kg
Initial velocity (u) = 0 m/s (since the drop is initially at rest)
Final velocity (v) = 50.0 m/s

Initial kinetic energy = (1/2) * 0.002 kg * (0 m/s)^2 = 0 J

Next, let's calculate the final kinetic energy of the drop just before it hits the ground. We can use the same formula for kinetic energy:

Final kinetic energy = (1/2) * mass * velocity^2

Final kinetic energy = (1/2) * 0.002 kg * (50.0 m/s)^2 = 0.05 J

Now, we can calculate the change in kinetic energy:

Change in kinetic energy = Final kinetic energy - Initial kinetic energy
= 0.05 J - 0 J
= 0.05 J

The work done by the resistive force is equal to the negative change in kinetic energy:

Work done by resistive force = - Change in kinetic energy
= - 0.05 J
= -0.05 J

Therefore, the correct answer is option 2: -12.50 J.