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2 years ago

If a ball is dropped from rest and falls 8 m to the ground, what is the speed just before it

Physics

1 answer:

Natalija [7]2 years ago

4 0

Answer:

12.5m/s

Explanation:

(Assuming the question was asking for the speed just before it hit the ground)

We can use the first key equation of accelerated motion

Vf^2 = Vi^2+2aΔd

Vf^2 = 0 + 2(9.8)(8) (plugged in values, initial velocity is 0 since the ball was at rest)

Vf^2 = 156.8

Vf = 12.5 (squared both sides)

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A 0.500 kg ball is dropped from rest at a point 1.20 m above the floor. The ball rebounds straight upward to a height of 0.700 m

KatRina [158]

To solve this problem we will apply the concepts related to energy conservation. With this we will find the speed before the impact. Through the kinematic equations of linear motion we will find the velocity after the impact.

Since the momentum is given as the product between mass and velocity difference, we will proceed with the velocities found to calculate it.

Part A) Conservation of the energy

$mgh = \frac{1}{2} mv^2$

$v_1 = \sqrt{2gh}$

$v_1 = \sqrt{2(9.8)(1.20)}$

$v_1 = 4.84m/s$

$\therefore v_1 = -4.84/s \rightarrow \text{Negative direction downward}$

Part B) Kinematic equation of linear motion,

$v_2^2 = u_0^2 +2a\Delta y$

Here

v= 0 Because at 1.5m reaches highest point, so v=0

$0 = u_2^2 +2(-9.8)(0.7)$

$u_2 = 3.7m/s$

Therefore the velocity after the collision with the floor is 3.7m/s

PART C) Total change of impulse is given as,

$J = P_2 -P_1$

$J = mU_2-mV_1$

$J = m(U_2-V_1)$

$J = (0.5)(3.7-(-4.84))$

$J = 4.27kg \cdot m/s \rightarrow \text{Upward because is positive}$

6 0

4 years ago

When a ray of light passes at an angle to the normal from one material into another material in which its speed is higher?

Gnesinka [82]

I think your talking about refraction and if so the first medium it existed in before entering the second usually has the higher speed especially it the first medium is less denser than the second

4 0

4 years ago

A balsa wood raft is 1.50 m long, 1.00 m wide, and 0.120 m high. the density of balsa is 380 kg/m^3. what is the mass of the raf

topjm [15]

Answer:

the mass of the raft is 68.4 kg

Explanation:

Since Mass is defined as Volume times Density, start by calculating the volume of the raft:

Volume = length x width x high = 1.5 m x 1.0 m x 0.12 m = 0.18 m^3

and now multiply it times the given density in order to find its mass:

Mass = Volume x Density = 0.18 m^3 x 380 kg/m^3 = 68.4 kg.

Notice that the m^3 units cancel out (they are in numerator and in denominator) leaving just the kg (a unit of mass) in the answer.