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3 years ago

7

A strong-armed physics student throws a tennis ball vertically. The ball stays in the air for 5.5 seconds. Assuming the ball lef

t from the ground, how fast did it leave his hand?

1 answer:

Mila [183]3 years ago

4 0

Answer:

27.5 m/s

Explanation:

applying motion equations we can find the answer,

v = u + a*t

Let assume ,

u = starting speed(velocity)

v = Final speed (velocity)

t = time taken for the motion

a = acceleration

by the time of reaching the highest point subjected to the gravity , the speed should be equal to zero (only a vertical speed component is there)

for the complete motion it takes 5.5 s. that means to reach the highest point it will take 5.5/2 =2.75 seconds

we consider the motion upwards , in this case the gravitational acceleration should be negative in upwards (assume g=10 m/s2)

that is,

v = 0 , a = -10 $ms^{-2}$ , t =2.75

v = u + at

0 = u -10*2.75

u = 27.5 $ms^{-1}$

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You are helping your friend move a new refrigerator into his kitchen. You apply a horizontal force of 275 N in the positive x di

Volgvan

Answer:

f = 347.08 N

Explanation:

The frictional force exerted by the floor on the refrigerator is given as follows:

$f = \mu R = \mu W$

where,

f = frictional force = ?

μ = coefficient of static friction = 0.58

W = Weight of refrigerator = mg

m = mass of refrigerator = 61 kg

g = acceleration due to gravity = 9.81 m/s²

Therefore,

$f = \mu mg\\f = (0.58)(61\ kg)(9.81\ m/s^2)\\$

<u>f = 347.08 N</u>

8 0

3 years ago

You create a ramp using two text books and a 0.50m board. Using a timer you determine that a cart can roll down the ramp in 0.55

ahrayia [7]

Answer:

The velocity of the cart at the bottom of the ramp is 1.81m/s, and the acceleration would be 3.30m/s^2.

Explanation:

Assuming the initial velocity to be zero, we can obtain the velocity at the bottom of the ramp using the kinematics equations:

$v=v_0+at\\\\v^2=v_0^2+2ad$

Dividing the second equation by the first one, we obtain:

$v=\frac{v_0^2+2ad}{v_0+at}$

And, since $v_0=0$ , then:

$v=\frac{2ad}{at}\\\\v=\frac{2d}{t}\\\\v=\frac{2(0.50m)}{0.55s}\\\\v=1.81m/s$

It means that the velocity at the bottom of the ramp is 1.81m/s.

We could use this data, plus any of the two initial equations, to determine the acceleration:

$v=v_0+at\\\\\implies a=\frac{v}{t}\\\\a=\frac{1.81m/s}{0.55s}\\\\a=3.30m/s^2$

So the acceleration is 3.30m/s^2.

7 0

3 years ago

What term is defined as the amount of charge stored per volt?

Shtirlitz [24]

Capacitance is a measure of charge stored per volt.

3 0

3 years ago

Read 2 more answers

A car travels from Boston to Hartford in 4 hours. The two cities are 240 kilometers apart. What was the average speed of the car

Y_Kistochka [10]

Answer:

Average speed is 60 km/hour

Explanation:

When we need to calculate average speed, we use this equation:

$V = \frac{x_{f} - x_{o}}{t_{f} - t_{o}}$

Where: $x_{o} = 0 km$ position at the beginning

$x_{f} = 240 km$ at the end

$t_{o} = 0 hours$

$t_{f} = 4 hours$

Then: $V = \frac{240 km - 0 km}{4 hours - 0 hours}$

$V = \frac{240 km}{4 hours}$

Finally V = 60 km/hour

6 0

3 years ago

What is the % error in using g = 10.0 m/s^2? (Take the value ofg as 9.8 m/s^2)

Alenkasestr [34]

Answer:

So percentage error will be 2 %

Explanation:

We have given initial value of acceleration due to gravity $g=10m/sec^2$

And final value of acceleration due to gravity $g=9.8m/sec^2$

We have to find the percentage error

We know that percentage error is given by $percentage\ error=\frac{initial\ value-final\ value}{initial\ value}\times 100$

So $percentage\ error=\frac{10-9.8}{10}\times 100=2$ %

4 0

3 years ago