Question

A body projected with a speed 20 ms at an angle 600 with horizontal. Its speedwhen it is | moving at an angle 300 with horizontal in ms-1 is​

Answer 1

Answer:

Answer

Correct option is

B

40  

3

​

 m

Given that,

Speed u=20m/s

Angle θ=30  

0

 

Height h=40m

Now, along y axis

 u  

y

​

=usin30  

0

 

u  

y

​

=20×  

2

1

​

 

u  

y

​

=10m/s

Now, we know that

 a=−10m/s  

2

 

s=−40m

Now, from equation of motion

 s=u  

y

​

t−  

2

1

​

gt  

2

 

−40=10t−5t  

2

 

5t  

2

−10t−40=0

t  

2

−2t−8=0

t  

2

−(4−2)t−8=0

t(t−4)+2(t−4)=0

(t+2)(t−4)

Now, neglect of negative value

So, t=4s

Now, the range is

 R=ucos30  

0

×t

R=20×  

2

3

​

 

​

×4

R=40  

3

​

m

Hence, the range is 40  

3

​

m

 

Explanation: