Question

A car falls off a ledge and drops to the ground in 0.5 s. Let g = 10 m/s2 .
1. What is the initial velocity of the car?
(a) 0 m/s
(b) 5 m/s
(c) 10 m/s
(d) none of these
2. What is its speed on striking the ground?
(a) 0 m/s
(b) 5 m/s
(c) 10 m/s
(d) none of these​

Answer 1

Given,

time taken=0.5s

g=10ms−2

As the car is under free fall, the initial speed is zero.

(a) Under free fall, 

u=0 

a=g

v=u+at

v=0+10×0.5

v=5ms−1

(b) Average speed = 2u+v=20+5=2.5ms−1

(c) From newton's equation of motion, As u=0,

h=ut+21gt2

When h is the height, t is the time of free fall, g is the acceleration due to gravity. Putting the values in the above equation, we get

h=21×10×(0.5)2=5×0.25=1.25m

Answer 2

Answer:

1. (a) 0 m/s (taking that car was stationary)

2.(b) 5 m/s

Explanation:

2.(b) -->

a = v-u/t

10 = v-0/0.5

5=v-0

v= 5 m/s