The vertical force exerted on the lawn is 68.8 N downward
Explanation:
The vertical force exerted by the lawnmower on the lawn is equal to the vertical component of the force applied, therefore:

where
F is the magnitude of the force applied
is the angle between the direction of the force and the horizontal
In this problem:
F = 120 N
Substituting,

where the negative sign means the direction of the force is downward.
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Answer:
initial magnetic field 1.306 T
Explanation:
We have given area of the conducting loop 
Emf induced = 1.2 volt
Initial magnetic field B = 0.3 T
Time dt = 0.087 sec
We know that induced emf is given by 


So initial magnetic field = 1.606-0.3= 1.306 T
Answer:
the number density of the protons in the beam is 3.2 × 10¹³ m⁻³
Explanation:
Given that;
diameter D = 2.0 mm
current I = 1.0 mA
K.E of each proton is 20 MeV
the number density of the protons in the beam = ?
Now, we make use of the relation between current and drift velocity
I = MeAv ⇒ 1 / eAv
The kinetic energy of protons is given by;
K = 
v²
v = √( 2K /
)
lets relate the cross-sectional area A of the beam to its diameter D;
A =
πD²
now, we substitute for v and A
n = I /
πeD² ×√( 2K /
)
n = 4I/π eD² × √(
/ 2K )
so we plug in our values;
n = ((4×1.0 mA)/(π(1.602×10⁻¹⁹C)(2mm)²) × √(1.673×10⁻²⁷kg / 2×( 20 MeV)(1.602×10⁻¹⁹ J/ev )
n = 1.98695 × 10¹⁸ × 1.6157967 × 10⁻⁵
n = 3.2 × 10¹³ m⁻³
Therefore, the number density of the protons in the beam is 3.2 × 10¹³ m⁻³
Answer:
The angular speed of the Crab nebula pulsar is 190.3 rad/s.
Explanation:
Given that,
Time T= 33 ms = 0.033 s
The angular speed is equal to the 2π divided by time period.
We need to calculate the angular speed of the Crab nebula pulsar
Using formula of angular speed

Where, T = time
= angular speed
Put the value into the formula


Hence, The angular speed of the Crab nebula pulsar is 190.3 rad/s.