10.to crack the whip<非正式>行使权威；(尤指)威逼某人苦干
11.to get cracking<非正式>(start)开始；动手
You'd better get cracking, the sooner the better.你应该动手了, 越快越好。
(hurry)赶紧；赶快
Vouchers must be redeemed before September 14th so you'd better get cracking to cash in.优惠券必须在9月14日之前兑换, 你最好抓紧点。