Question

A constant retarding force of 20N acts on a body of mass 5 kg moving initially with a
speed of 10 ms ! How long does the body take to stop?​

Answer 1

Answer:

It takes 6s for body to stop. since it is retardation then acceleration become negative. therefore a= -2.5 m/s^2. It takes 6s for body to stop.

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Answer 2

Answer:

It takes 2.5 seconds for body to stop.

Step-by-step explanation:

Given,

• Force = 20 N
• Mass = 5 kg
• Speed = 10 m/s

Retardation (a) = Force(F) / Mass(m)

which means,

a = F/m

⇒ a = 20/5

⇒ a = 4 m/s²

∵ It is retardation, acceleration become negative.

∴ a = -4 m/s²

Now,

Final Velocity(v) = Initial Velocity(u) + (Acceleration(a) ×Time(t))

Which means,

v = u + at

Here,

• Final Velocity(v) = 0 m/s
• Initial Velocity(u) = 10 m/s
• Acceleration(a) = -4 m/s²

⇒ 0 = 10 + (-4) t

⇒ t = 10/4

⇒ t = 2.5 seconds

∴ It takes 2.5 seconds for body to stop.