Question

A constant force acts on a body of mass 0.9kg at rest for 10s. if the body
250m, the magnitude of the force is
b) 3.5N
c) 4N
d)4.5N​

Answer 1

Given :-

◉ A constant force acts on a body of mass, m = 0.9 kg which is at rest for t = 10s.

◉ As a result, the body displaces about s = 250m.

To Find :-

◉ The magnitude of the force

Solution :-

The initial velocity of the body is u = 0 m/s (given body is at rest), And the displacement made by the body is 250m

Using second equation of motion, we have

⇒ s = ut + 1/2 at²

⇒ 250 = 0×10 + 1/2 × a × 10²

⇒ 250 = 50a

⇒ a = 5 m/s² ...(2)

We know,

⇒ Force = Mass × Acceleration

⇒ Force = m × 5 [ from (2) ]

⇒ Force = 0.9 × 5

⇒ Force = 4.5N

So, The magnitude of force is 4.5 N

∴ Option (D) is correct.

Some Information :-

☛ Impulse is the force applied per unit time.

Impulse = Force / Time

☛ Other equations of motion:

• 1st : v = u + at
• 3rd : 2as = v² - u²

☛ Acceleration is the rate of change of velocity per unit time.

• Velocity is the rate of change of displacement per unit time.
• Displacement is shortest path length between final and initial position