Question

A car of mass 400 kg moving at a speed of 20 m/s is brought to rest in 20 s by a constant retarding force. Calculate the retarding force.​

Answer 1

✬ Retàrding Force = 400 N ✬

Explanation:

Given:

• Mass of car is 400 kg.
• Initial speed of car is 20 m/s.
• Time taken to brought in rest is 20 s.
• Final velocity is 0.

To Find:

• Retarding force ?

Formula to be used:

• Force = mass × acceleration
• Acceleration = (v – u/t)

Solution: Here we have

• u = 20 m/s
• v = 0
• t = 20 s
• m = 400 kg

➟ So, acceleration = (v – u/t)

➟ a = (0 – 20/20)

➟ a = –20/20 = –1 m/a²

Substituting value on formula

$\implies{\rm }$ F = m × a

$\implies{\rm }$ F = 400 × –1

$\implies{\rm }$ F = –400 N

(Negative sign shows that force is retarding)

Hence, retarding force will be 400 N.

• S.I unit of force is Newton. It is denoted by capital N.

Answer 2

 Retàrding Force = 400 N 

Explanation:

Given:

Mass of car is 400 kg.

Initial speed of car is 20 m/s.

Time taken to brought in rest is 20 s.

Final velocity is 0.

To Find:

Retarding force ?

Formula to be used:

Force = mass × acceleration

Acceleration = (v – u/t)

Solution: Here we have

u = 20 m/s

v = 0

t = 20 s

m = 400 kg

➟ So, acceleration = (v – u/t)

➟ a = (0 – 20/20)

➟ a = –20/20 = –1 m/a²

Substituting value on formula

\implies{\rm }⟹ F = m × a

\implies{\rm }⟹ F = 400 × –1

\implies{\rm }⟹ F = –400 N

(Negative sign shows that force is retarding)

Hence, retarding force will be 400 N.

S.I unit of force is Newton. It is denoted by capital N.