Answer:
Toward the north, 300 N
Explanation:
Consider the upward direction as positive and downward direction as negative.
Given:
Mass of the balloon is, 
Lift force on the balloon in the upward direction is, 
Take acceleration due to gravity as 10 N/kg.
Now, weight of the balloon acting downward is given as the product of its mass and acceleration due to gravity. Therefore,
Weight is, 
Now, net force is given as the vector sum of both the forces.

The upward direction is the direction of North. So, the net force acting on the balloon is 300 N towards North.
Given :
Mass of person, m = 81 kg.
Area of high heal, A = 3.5 cm² = 0.00035 m².
To Find :
The pressure applied by the heal on the ground.
Solution :
We know, pressure is given by :

Hence, this is the required solution.
Answer:
Few millimeter thick aluminium, water, wood, acrylic glass or plastic.
Explanation:
The materials that are best for protection against beta particles are few millimeter thickness of aluminium, but for the high energy beta-particles radiations the low atomic mass materials such as plastic, wood, water and acrylic glass can be used.
These materials can also be used in personal protective equipment which includes all the clothing that can be worn to prevent any injury or illness due to the exposure to radiation.
Answer:
787528.7 J
Explanation:
Work done: This can be defined as the product of force and distance along the direction of force. The S.I unit of work is Joules (J).
From the question,
W = Tcos∅(d)............. Equation 1
Where W = work done, T = tension in the rope, ∅ = the angle of the rope to the horizontal, d = distance.
But,
d = v(t)..................... equation 2
Where v = velocity, t = time
Substitute equation 2 into equation 1
W = Tcos∅(vt)............. Equation 3
Given: T = 210 N, ∅ = 23°, v = 7 km/h = 1.94 m/s, t = 35 min = 2100 s
Substitute into equation 3
W = 210(cos23°)(1.94×2100)
W = 787528.7 J