Question

Q1. A body of weight W is resting on a frictional surface. The angle between the force of friction and normal reaction is.
a). 0
b).30
c).60
d).90
Q2. Maximum range of a projectile is 10 m What will be it's maximum range if it's velocity of projection is Doubled??
a).20m
b).30m
c). 40m
d).45m​

Answer 1

Answer:

See the above solution.

Answer 2

Q 1 ; it has given that, weight of a body = W , it is resting on a frictional surface.

normal reaction acts just opposite of weight of body. [ from Newton's 3rd law ]

so direction of normal reaction must be upward if direction of weight is downward.

but force of friction acts on the contacting surface and it directes opposite of relative motion of body.

so the angle between force of friction and normal reaction would be 90° [ see diagram ]

Q 2 : it has given that, maximum range of a projectile, R = 10m

maximum Range, R = u²/g

it is clear that maximum range is directly proportional to u²

so, R₁/R₂ = (u₁/u₂)²

⇒10/R₂ = (u/2u)²

⇒R₂ = 40 m

Therefore the maximum range of projectile would be 40 m if velocity of projection is doubled.