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2 years ago

6

Which of these shows unbalanced forces at work on an object? A. an ice skater turning as he skates around an ice rink B. a bicyc

le chained to a bike rack at school C. a car driving at a constant 25 miles per hour on a straight street D. a water skier pulled by a boat at a constant 30 mph

2 answers:

Serggg [28]2 years ago

5 0

The answer is A people think ok..................................................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

rosijanka [135]2 years ago

4 0

I’m pretty sure the answer is a

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A packing crate with mass 80.0 kg is at rest on a horizontal, frictionless surface. At t = 0 a net horizontal force in the +x-di

Nataly [62]

Answer:

Final speed of the crate is 15 m/s

Explanation:

As we know that constant force F = 80 N is applied on the object for t = 12 s

Now we can use definition of force to find the speed after t = 12 s

$F . t = m(v_f - v_i)$

so here we know that object is at rest initially so we have

$80 (12) = 80( v_f - 0)$

$v_f = 12 m/s$

Now for next 6 s the force decreases to ZERO linearly

so we can write the force equation as

$F = 80 - \frac{40}{3} t$

now again by same equation we have

$\int F .dt = m(v_f - v_i)$

$\int (80 - (40/3)t) dt = 80(v_f - 12)$

$80 t - \frac{40t^2}{6} = 80(v_f - 12)$

put t = 6 s

$480 - 240 = 80(v_f - 12)$

$v_f = 12 + 3$

$v_f = 15 m/s$

6 0

2 years ago

1. California sea lions can swim as fast as 40.0 km/h. Suppose a sea lion begins to chase a fish at this speed when the fish is

Pie

#1

In order to chase the fish the distance traveled by sea lion in time t must be equal to the distance of sea lion from the fish and distance traveled by fish in the same time.

So here we can say let say sea lion chase the fish in time "t"

then here we have

$d_1 = d_2 + L$

here

d1 = distance covered by sea lion in time t

d2 = distance covered by fish in the same time t

L = distance between fish and sea lion initially = 60 m

$d_1 = v_1 * t$

$d_1 = (40*\frac{5}{18})*t = \frac{100}{9}*t$

$d_2 = (16*\frac{5}{18})*t = \frac{40}{9}*t$

$\frac{100}{9}*t = \frac{40}{9}*t + 60$

$\frac{100}{9}*t - \frac{40}{9}*t = 60$

$\frac{60}{9}*t = 60$

$t = 9 s$

So it will take 9 s to chase the fish by sea lion

# 2

velocity of truck on road = 25 m/s along North

velocity of dog inside the truck = 1.75 m/s at 35 degree East of North

$v_{dt} = 1.75 cos35\hat j + 1.75sin35 \hat i$

$v_{dt} = 1.43 \hat j + 1 \hat i$

we can write the relative velocity as

$v_d - v_t = 1.43 \hat j + 1 \hat i$

$v_d = v_t + (1.43 \hat j + 1 \hat i)$

now plug in the velocity of truck in this

$v_d = 25 \hat j + (1.43 \hat j + 1 \hat i)$

$v_d = 26.43 \hat j + 1 \hat i$

so it is given as

$v_d = \sqrt{26.43^2 + 1^2} = 26.44 m/s$

direction will be given as

$\theta = tan^{-1}\frac{v_x}{v_y}$

$\theta = tan^{-1}\frac{1}{26.43} = 2.2 degree$

so with respect to ground dog velocity is 26.44 m/s towards 2.2 degree East of North

8 0

2 years ago

Read 2 more answers

Ferns that eject spores generally do so in pairs, with two spores flying off in opposite directions. The structure from which th

Furkat [3]

Answer:

It cancels recoil.

Explanation:

For each action there is an equal an opposite reaction.

The principle of conservation of momentum tell us that if a single spore were ejected the fern would suffer a recoil from it. This recoil would take energy and speed from the spore. But if they are ejected in pairs the recoil is canceled and all the energy is transferred to the spores resulting in higher speeds.

5 0

2 years ago

Have you ever chewed on a wintergreen mint in front of a mirror in the dark? If you have, you may have noticed some sparks of li

lutik1710 [3]

Answer:

Part a)

$E = 3.66 eV$

Part b)

$\lambda = 508.5 nm$

Explanation:

Part a)

change in the energy due to decay of photon is given as

$E = h\nu$

here we know that

$\nu = 8.88 \times 10^{14} Hz$

now we have

$E = (6.6 \times 10^{-34})(8.88 \times 10^{14})$

$E = 5.86 \times 10^{-19} J$

$E = 3.66 eV$

Part b)

While electron return to its ground state it will emit a photon of energy 2/3rd of the total energy

so we have

$\Delta E = \frac{2}{3}(3.66 eV)$

$\Delta E = 2.44 eV$

now to find the wavelength we have

$\Delta E = \frac{hc}{\lambda}$

$2.44 = \frac{1242}{\lambda}$

$\lambda = 508.5 nm$

3 0

2 years ago

A 60 kilogram astronaut weighs 96 newtons on the surface of the moon. calculate the acceleration due to gravity on the moon.

34kurt

Given: Mass m = 60 Kg

Weight W = 96 N

Required: Acceleration due to gravity, g = ?

Formula: W = mg

g = W/g

g = 96 Kg.m/s²/60 Kg (note: this is the derive unit for Newton "N")

g = 1.6 m/s²

6 0

2 years ago

Read 2 more answers