Given the time, the final velocity and the acceleration, we can calculate the initial velocity using the kinematic equation A:

A skateboarder flies horizontally off a cement planter. After a time of 3 seconds (Δt), he lands with a final velocity (v) of −4.5 m/s. Assuming the acceleration is -9.8 m/s² (a), we can calculate the initial velocity of the skateboarder (v₀) using the kinematic equation A.

Given the time, the final velocity and the acceleration, we can calculate the initial velocity using the kinematic equation A:

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The correct answer is
<span>c. one person exerts more force than the other so that the forces are unbalanced.
In fact, the door is initially at rest. In order to move the door, a net force different from zero should be applied, according to Newton's second law:
</span>

<span>where the term on the left is the resultant of the forces acting on the door, m is the door mass and a its acceleration.
In order to move the door, the acceleration must be different from zero. But this means that the resultant of the forces acting on it must be different from zero: this is possible only if the forces applied by the two persons are unbalanced, i.e. one person exerts more force than the other.</span>
Answer:
Given
acceleration (a) =1.5ms2
Force(F) =2100N
R. t. c mass (m) =?
Form
F=ma(divided by m both sides)
m=F/a
m=2100/105
m=1400kg
mass of car =1400kg
The image mentioned is in the attachment
Answer: a) P = 2450 Pa;
b) P = 2940 Pa;
c) F = 4.9 N
Explanation:
a) Pressure is a force applied to a surface of an object or fluid per unit area.
The image shows a block applying pressure on the large side of the piston. The force applied is due to gravitation, so:
P = 
P = 
P = 
P = 2450 Pa
The pressure generated by the block is P = 2450 Pa.
b) A static liquid can also exert pressure and can be calculated as:
ρ.g.h
where
ρ is the density of the fluid
h is the depth of the fluid
g is acceleration of gravity
600.9.8.0.5
2940 Pa
The pressure in the fluid at 50 cm deep is
2940 Pa.
c) For the system to be in equilibrium both pressures, pressure on the left side and pressure on the right side, have to be the same:

= 
F = 
Adjusting the units,
= 0.002 m².
F = 
F = 4.9 N
The force necessary to be equilibrium is F = 4.9 N.
Answer:
- 210 rad/s²
Explanation:
n = frequency of rotation = 3400/60 = 170/3 per sec.
angular velocity ω ( 0 ) at time 0 = 2π n = 2π x 170/3
angular velocity at time t = ω(t) = 0
now, ω²( t) = w²(o) + 2α Φ ( α = angular acceleration and Φ = angular displacement) = 2π x 48 rad.
0 = ( 2π x 170/3 )² + 2α x 48 x 2π
α = - (2π x 170 x 170 )/ (3 x 3 x 2 x 48 ) = 210 rad / s²