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Standard IX

Physics

Derivation of Velocity-Time Relation by Graphical Method

Given v=0 ...

Question

Given
$v = 0$ $m / s$
$u = 15 m / s$
$a = - 2.5$ $m s^{- 2}$
$t = ?$

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Solution

$v = u + a t$
$v = 0$
$u = 15 m / s$
$a = - 2.5 m / s^{2}$
$0 = 15 - 2.5 \times t$
$15 = 2.5 t$
$t = \frac{15}{2.5}$ = $6 s$

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Similar questions

A constant retarding force of 50N is applied to a body of mass 20kg moving with the speed of 15m/s. How long does the body take to stop?

Ans1 Given

F=50N

M=20kg

u=15m/s

v=0

As F=ma

a=50/20=2.5m/s^2

Since the retarding is negativd so -2.5 m/s^2

Time=

v=u+at

=0-15/-2.5=6s

Ans2 F=ma

50=20×0-15/t

50=20×-15/t

50/20×-15=1/t

-6 s=t

Why the 2 is incorrect ?

Q. From Points

A

and

B

, at height of

2 m

and

6 m

, two bodies are thrown simultaneously towards each other; one is thrown horizontally with a velocity of

8 m/s

and the other downwards at an angle of

45^{\circ}

to the horizontal at an initial velocity such that the bodies collide in flight. The horizontal distance between points

A

and

B

8 m

. Calculate
a) The initial velocity

u_{0}

of the body thrown at an angle of

45^{\circ}

b) The times of flight

t

of the bodies before collision
c) Velocities

v_{A}

and

v_{B}

of the two bodies at the instant of collision. The trajectories lie in a single plane.

Q. Michael Jordan has a vertical leap of 1.25 m. What is his takeoff speed and for how much time he will be in the air? Take a =

10 m s^{- 2}

downwards.

Complete the following table:

(A)

u (m/s)	a (m/s²)	t (sec)	v = u + at (m/s)
0	5	5	----
---	1	8	16

(B)

u (m/s)	a (m/s²)	t (sec)
4	10	2	---
16	---	5	105

(C)

u (m/s)	a (m/s²)	s (m)	v² = u² + 2as (m/s)
3	5	---	7
---	2	11	12

Michael Jordan has a vertical leap of 1.25 m, what is his takeoff speed and for how much time he will be in the air? Take $g = 10 m s^{- 2}$ .

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Givenv=0 m/su=15m/sa=−2.5 ms−2t=?

v=u+atv=0u=15m/sa=−2.5m/s20=15−2.5×t15=2.5tt=152.5=6s

Given
$v = 0$ $m / s$
$u = 15 m / s$
$a = - 2.5$ $m s^{- 2}$
$t = ?$

$v = u + a t$
$v = 0$
$u = 15 m / s$
$a = - 2.5 m / s^{2}$
$0 = 15 - 2.5 \times t$
$15 = 2.5 t$
$t = \frac{15}{2.5}$ = $6 s$