Question 172: Motion in 2D & Vectors

Question

A car starts from rest and accelerates at 5m/s
2
. At t = 4 s, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at t = 6 s? (Take g = 10 m/s
2
)

Accepted Answer

u = 0
a = 5
t = 4
velocity of car at t = 4 sec is
V = u + at
V = 0 + 5 $$	imes$$ 4
V = 20 m/s
For ball :
At t = 4 s, A ball is dropped out of a window so
velocity of ball at this instant is 20 msÃ¢ÂÂ1 along
horizontal.
After 2 seconds of motion :
Horizontal velocity of ball , V
x
= 20 m/sec
V
y
= u + ut
= 10 $$	imes$$ 2
Vertical velocity of ball, V
y
= 20 m/sec
So magnitude of velocity of ball
V = $$\sqrt {V_x^2 + V_y^2} $$ =  20$$\sqrt 2 $$
and Acceleration of ball at t = 6 s is g = 10 m/sec
2
As ball is under free fall.

Answer

20$$\sqrt 2 $$ m/s, 10 m/s
2

Answer

20 m/s, 5 m/s
2

Answer

20 m/s, 0

Answer

20$$\sqrt 2 $$ m/s, 0

Motion in 2D & Vectors

A car starts from rest and accelerates at 5m/s 2 . At t = 4 s, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at t = 6 s? (Take g = 10 m/s 2 )

Choose the correct answer: