Question

A 2,000-kilogram car uses a braking force of 12,000 Newton to stop in 5 seconds. What is its initial speed of the car?

Answer 1

First, solve for the acceleration of the car. You know the mass of the car and the braking force, so you can use the equation Force = Mass x Acceleration. This gives you 12,000 = 2,000 x A. Divide 12,000 by 2,000 to find the acceleration equal to 6 m/s^2. This is the rate that the car is slowing down at. Velocity is equal to accleration x time (rate x time), so you multiply 6 by the time of 5 seconds. This leaves you with a velocity of 30 m/s or about 67.1 mph.

Answer 2

Answer: The initial speed of the car is 30 m/s

Explanation:

Force is defined as the push or pull on an object with some mass that causes change in its velocity.

It is also defined as the mass multiplied by the acceleration of the object.

Mathematically,

$F=m\times a$

where,

F = force exerted on the car = 12,000 N

m = mass of the car = 2,000 kg

a = acceleration of the car = ?

Putting values in above equation, we get:

$12000kg.m/s^2=2000kg\times a\\\\a=\frac{12000}{2000}=6m/s^2$

• To calculate the initial speed of the car, we use first equation of motion:

$v=u+at$

where,

v = final speed of the car = 0 m/s   (brakes are applied)

u = initial speed of the car = ?

a = acceleration of the car = $-6m/s^2$   (as the car is getting stopped)

t = time taken = 5 sec

Putting values in above equation, we get:

$0=u+(-6\times 5)\\\\u=0+30\\\\u=30m/s$

Hence, the initial speed of the car is 30 m/s