Question

A car falls off a ledge and drops to the ground in 0.5 s. Take g=10.

What is its speed on striking the ground?

How high is the ledge from the ground?

Answer 1

Explanation:

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 =

2

u+v

=

2

0+5

=2.5ms

−1

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

h=ut+

2

1

gt

2

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=

2

1

×10×(0.5)

2

=5×0.25=1.25m

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