The speed of an object at the end of 4 successive seconds is 20, 25, 30, 35 mph km/hr

The speed of an object at the end of 4 successive seconds is 20, 25, 30, 35 mph km/hr respectively the acceleration of the object is: 

a) 5m/s^2 

b) 5km/hr^2 

c) 5km/hr/s 

d) 5k sec^2


Solution

The acceleration can be calculated by taking the difference in velocity and dividing by the time interval. Here, the time interval is 4 seconds, so the acceleration can be found as follows:

(35 mph - 20 mph)/4 seconds = 15 mph/4 seconds = 3.75 mph/sec

So, the acceleration is approximately 3.75 km/hr/s, or 5 km/hr/s (rounded to the nearest whole number).

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Two electric point charges of equal size are 15 cm apart and interact with a force of 8.1 N ...

Two electric point charges of equal size are 15 cm apart and interact with a force of 8.1 N. What is the modulus of these charges?

Solution

The modulus of the electric charges can be calculated using Coulomb's law: 

F = k * q1 * q2 / d^2

where: 

F is the interaction force

k is the Coulomb constant (8.99 x 10^9 N * m^2 / C^2)

q1 and q2 are the values of the point charges, and d is the distance between them.

If we solve this equation for q1 and q2, we get: 

q1 = q2 = sqrt(F * d^2 / k) = sqrt(8.1 N * (0.15 m)^2 / 8.99 x 10^9 N * m^2 / C^2) = 8.98 x 10^-19 C.

So, the modulus of the charges is approximately 8.98 x 10^-19 C.

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300 g Aluminum with 90% purity reacts with an HCl solution of C % = 40. It is required ...

300 g Aluminum with 90% purity reacts with an HCl solution of C % = 40. It is required: 

a) Chemical reaction equation; 

b) pure aluminum mass; 

c) ms HCl; d)VH2 for p=1.5 atm and T=27 • C; 

e) Cm=?;


Solution

a) Al + HCl → AlCl3 + H2

b) 300g * 90% purity = 270g

c) ms HCl = C% * m solution / 100 = 40% * m solution / 100

d) VH2 = nH2 * R * T / p = (ms Al / MAl) * R * T / p, where n is the number of moles of H2, R is the gas constant, T is the temperature in Kelvin, and p is the pressure.

e) Cm = ms solute / m solution = ms AlCl3 / m solution

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What is the speed of sound in air at 20 centigrade?

What is the speed of sound in air at 20 centigrade?

Solution

The speed of sound in air is approximately 343 meters per second (m/s) or 1235 kilometres per hour (km/h) at 20 degrees Celsius (68°F).

Physics problems from users and solved