Question

A car falls off a bridge and drops to the ground in 1.5s

(i) What is its speed on striking the ground?

(ii) What is its average speed during 1.5 s?

(iii) How high is the bridge from the ground?​

Answer 1

Explanation:

of 13000 kg in each second. The exhaust gases rush out at 2500 m/

Answer 2

Given:

Since the car just falls off,

Initial velocity (u) = 0 m/s,

Acceleration = 10 m/$s^{2}$ (Gravitational Force)

Time (t) = 1.5 s

To Find:

(i) Speed on striking the ground.

(ii) Average speed during 1.5 s.

(iii) Height from the ground.

Solution:

(i) Speed of a car on striking the ground is nothing but the final velocity of a car, that is v

We know the first equation of motion,

        v = u + at      

using this equation we will find the value of v as:

        v = 0 + 10 x 1.5

        v = 15 m/s

Hence, the speed of a car on striking the ground is 15 m/s.

(ii) Now, let's find the average speed:

Average Speed = $\frac{initialvelocity + final velocity}{2}$

                           = $\frac{u+v}{2}$

                           = $\frac{0+15}{2}$

Average Speed = 7.5 m/s

Hence, the average speed of a car is 7.5 m/s.

(iii) Height of the bridge from the ground:

Here, the height of the bridge will be the distance traveled, that is s

We know the second equation of motion,

        s = ut + $\frac{1}{2}$a$t^{2}$

        s = 0 x 1.5 + $\frac{1}{2}$ x 10 x $1.5^{2}$

        s = 0 + 5 x 2.25

        s = 11.25 m

Hence, bridge is 11.25m high from ground.