Question

1) A car accelerates at 4 m /s / s. Assuming the car starts from rest, how far will it travel in 10 s?

2) An object falls freely from rest on a planet where the acceleration due to gravity is twice that of in Earth. Find the speed of the object after 5 second?

3) It takes 8 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?

4) A bag of groceries has a mass of 30 kilograms and in earth. Find its weight in the earth in moon?

5) If two force vector 20N and 40N are perpendicular to each other. Find the resultant vector?

Answer 1

1) D = d(initial position) + v*t (initial velocity times time) + (1/2)a*t^2 (.5 times acceleration times time squared)

Your initial position and velocity are both zero, so the first two terms drop out of this problem, and you’re left with

D = 1/2at^2 = 200 m

2) v = u + at = 0 + 2*9.8*5 = 98 m/s

3) Using d = (1/2) g t2 = (1/2)(9.8)(64) = about 313.6 m

4)

The mass of the moon is 0.0123 of Earth's, and its radius is 0.273 of Earth's. To find the gravitational pull on the moon compared to Earth's, we put those numbers in the formula:

(ratio of masses)/(ratio of radii)^2

= 0.0123/(0.273)^2 = 0.165, which is approximately 1/6.

Thus, given any weight on the Earth's surface, you can divide by 6 to find its weight on the moon.

so , weight on the moon = 30/6 = 5 kg

5) It will be the square root of the sum of the squares of the the two forces. Thus, if R is the resultant, then R= square root of (20^2+40^2). Simply apply Pythagoras theorem

R= 44.72 N