Question

Please answer me . I want to full explanations ​

Answer 1

Question: velocity-time graph of a mass 2 kg moving in a straight line as shown in the figure. Workdone by all the forces is

(i) 400 J    (ii) - 400 J   (iii) - 200 J  

Answer:

- 400 J

Step-by-step explanation:

At t = 0,  u(velocity) = 20 m/s

At t = 2,  v(velocity) = 0 m/s

   Using, the equation of motion,

⇒ v = u + at

⇒ 0 = 20 + a(2)   ⇒ - 10 = a

 Therefore,

⇒ v² = u² + 2aS

⇒ 0² = (20)² + 2(-10)S

⇒ 20 = S

∴ Workdone = force x displacement

                  = ma x S

                  = (2)(-10) x 20

                  = - 400 J

Answer 2

Required answer:-

Question:

• Velocity-time graph of a particle of mass 2kg moving in a straight line. Work done by all the forces on the particle is

(1) 400 J

(2) -400 J

(3) -200 J

(4) 200 J

Solution:

Given,

• Mass of particle which is moving in a straight line = 2kg

To find:

• Work done by the forces on particle

Equation of motion used:

• v = u + at

Step by step explaination:

As, we know

t = 0, u (velocity) = 20 m/s

and

t = 2 , u (velocity) = 0 m/s

Now,

v = u + at

0 = 20 + a(2)

-20 = a(2)

a = -20/2

a = -10

v² = u² + 2aS

( S is displacement )

0² = (20)² + 2(-10)S

0 = 400 - 20S

20 S = 400

S = 400/20

S = 20

As, we know

Work done = force × displacement

So,

Work done = (2)(-10) × 20

= -20 × 20

= -400 J

Therefore work done by the forces on particles is -400J