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A car falls off a ledge and drops to the...

A car falls off a ledge and drops to the ground is 0.5s Let `g=10ms^(-2)` (for simplifying the calculations).
(i) What is its speed on striking the ground?
(ii) What is its average during the 0.5s?
(iii) How high is the ledge from the ground?

Text Solution

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Time `t=1/2 s`
Initial velocity `u=0ms^(-1)`
Acceleration of the car `a=g=+10ms^(-2)` (downward)
(i) speed v=at
`v=10ms^(-2) xx 0.5 s=5ms^(-1)`
(ii) average speed `=(u+v)/2`
`=(0 ms^(-1) +5ms^(-1))/(2)=2.5ms^(-1)`
(iii) distance travelled, `s=1/2at^(2)`
`=1/2 xx 10 ms^(-2) xx (0.5s)^(2)`
`=1/2 xx 10ms^(-2) xx 0.25 s^(2)=1.25m`
Thus,
(i) its speed on striking the ground `=5ms^(-1)`
(ii) its average speed during the 0.5s `=2.5 ms^(-1)`
(iii) height of hte ledge from the ground =1.25m
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