Question

Please give these THREE problems step by step approach to solving

1) A 30 g steel ball is released from rest and falls vertically into a steel plate. The ball strikes the plate and is in contact with it for 0.5 ms. The ball rebounds elasticity, and returns to its original height. The time interval for a round trip is 4.00 s. In this situation, the average force exerted on the ball during contact wth the plate is closest to:

a)1570N b)1960N c)2750N d)2350N e)1180N

2)Three cars (car L, car M, and car N) are moving with the same velocity, and slam on the brakes. The most massive car is car L, and the least massive is car N. Assuming all three cars have identical tires, for which car is the amount of work done by friction in stopping it the highest?

a) The amount of work done by friction is the same for all cars b)Car L c)Car M d) Car N

3) if you stood on a planet having a mass four times higher than Earth's mass, and a radius two times longer than Earth's radius, you would weigh

a) two times more than you do on Earth b) two times less than you do on earth

c) four times more than you do on Earth d) the same as you do on Earth

Answer 1

1)

F = m (v₂ - v₁) / (delta) T

(v₂ - v₁) is the change in the velocity and = 2 * (velcity at the time of collission) = 2 (g *t) = 2* 9.8 * 2 = 39.2 m/s

F = 0.03 * 39.2 / 0.5 *10^-3 = 2352 N

Ans is (d) 2350 N

2)

Mass Variation :    M_L > M_M > M_N

Normal variation :   N_L > N_M > N_N

Friction variation :   f_L > f_M > f_N

work done by friiction :   W_L > W_M > W_N

car in which the amount of work done by friction in stopping it the highest is car L.

Ans is (b) Car L

3)

g = GM / R²     where G = 6.67384