Question

A car retards uniformly at the rate of 5 m/s² and stops in 10 s. The initial velocity of car is (a) 10 m/s (b) 5 m/s (c) 50 m/s (d) 25 m/s​

Answer 1

Answer:

the answer is c) 50 m/s

Explanation:

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Answer 2

Required Answer :

The initial velocity of the car = 10 m/s

Answer → (a) 10 m/s

Given :

• Retardation of a car = 5 m/s²
• Time taken by the car to stop = 10 s
• Final velocity = 0 m/s [Because the car comes to rest.]

To find :

• Initial velocity of the car = ?

Solution :

Here, in this question we need to calculate the initial velocity of the car. So, we will use the third equation of motion.

Third equation of motion :

• v² - u² = 2as

where,

• v denotes the final velocity
• u denotes the initial velocity
• a denotes the acceleration
• s denotes the time

we have,

• v = 0 m/s
• u = ?
• a = - 5 m/s² [Negative acceleration is know as retardation.]
• s = 10 s

Substituting the given values :

→ (0)² - u² = 2(-5)(10)

→ 0 - u² = - 100

→ - u² = - 100

→ u² = 100

→ Taking square root on both the sides :

→ u = √(100)

→ u = ± √(10) Reject - ve

→ u = 10

Therefore, the initial velocity of the car = 10 m/s