# Thread:

1. ## need help please (physics)

In college homecoming competition, 16 students lift sports car while holding the car off the ground, each student exerts an upward force of 400 N. (a) what is the mass of the car in kilograms? (b) what is its weight in pounds?

2. Originally Posted by twistedmexican
In college homecoming competition, 16 students lift sports car while holding the car off the ground, each student exerts an upward force of 400 N. (a) what is the mass of the car in kilograms? (b) what is its weight in pounds?
a) Each of the 16 students is exerting an upward force on the car and (I presume) the car is stationary and off the ground. So the students are supplying the only upward force, which is counteracting the weight of the car. Thus
$w = 16F = 16 \cdot (400~N) = 6400~N$
(where w is the weight of the car.)

So the mass of the car is
$m = \frac{w}{g} = \frac{6400~N}{9.8~m/s^2} = 653.061~kg$

b) 1 lb = 4.45 N, so
$\frac{6400~N}{1} \cdot \frac{1~lb}{4.45~N} = 1439.75~lb$

-Dan
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