Question

Problem 1: A student pushes a loaded sled whose mass is 240 kg to a distance of 2.3 m over the
frictioniess surface of a frozen lahe. Hic exerts a horizontal force equal to 130N. Ifthe sled starts from
rest, what is its final velocity ?


Problem 2. A constant force acting on a body of mass 3.0 kg changes its speed from 2.0 m/s to 3.5 m/s in
25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of
force?

Problem 3. A trolley of mass 1000 kg is moving with a speed of 5 m/s. Sand is dropped onto it at the rate
of 30 kg/min. What is the force needed to keep the trolley moving with a uniform speed?
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Answer 1

Answer:

Explanation:

1. V² - U² = 2 a S

ACCELERATION = 130/240 = 0.54 N

 V² - 0² =  2 * 0.54 * 2.3

V² = 2.5

V=  1.58 m/s²

2. V = U +a T

3.5 = 2 + a * 25

a = 0.06 m/s²

FORCE = MASS *a

= 3 * 0.06 = 0.18 N....DIRECTION OF FORCE IS SAME AS THAT OF DIRECTION OF MOTION

3. RATE OF CHANGE OF MOMENTUM = FORCE

$\d {dP}/ \, dT$ = FORCE

Δ m = 30 kg/ min = 0.5 kg/sec

CHANGE IN MOMENTUM = Δ m * v  = 0.5 * 5 kg /sec = 2.5 N

force required = 2.5 N